How to Do a PLCU

[Editor's Note: The past several posts have focused in one way or another upon a common challenge confronting physics teachers.  The challenge involves getting students involved, engaged and invested in minds-on activity during hands-on laboratory activities. This post represents one teacher's efforts to salt the oats.]



The desire to make laboratory experiences appear to be meaningful to students caused me to rethink some of the methods by which they were evaluated about a decade ago. The desire of students to merely complete a set of directions without incorporating the relationships they were investigating was such an abhorrence, as was the copying that ensued, that I decided to make each discovery experience one of responsibility; the students were going to learn something and were expected to apply it.

The method by which this was done became know as the “Post-Lab Check Up” (plcu). Its intention was to make each student responsible to observe/collect data and discover and apply relationships. Their observations and results were organized in some fashion (sheet, notebook…) which were then used while responding to the questions related to the investigation. The goal is not for the student to have a complete understanding of the concepts at hand, but to use previously-acquired skills in new situations and make some sense of them.

This may appear to be similar to a “lab quiz” format, but the intentions are different. The plcu is intended to keep the student engaged with the activities of his or her group, experiencing mutual discovery. Since I started doing this a little over 10 years ago, very infrequently does any student refrain from involvement, a surprising change from the days when one student would dominate while the others copied. The copying that occurs now is almost always followed by “what does this mean?” or “how did you find that?” a far cry from the blatant plagiarism of the past.

Although improvement in attitude in the laboratory is valuable in itself, the Post-Lab Check Up serves a second purpose. It is well known that investigation followed by rehearsal is much more effective in making sense of the concepts at hand than investigation alone. Therefore I try to have the “check up” occur during the same class period. When this is not possible, it will occur at the beginning of the next period. While this may appear to be valuable since students can then spend the next few hours reviewing what they discovered, it is a rare event when a student spends any meaningful time unless there is an evaluative piece to complete such as data analysis, graphing…. In these situations, having the check up the next day is required.

The purpose of the post-lab check up is to provide a low key, non-intimidating experience for students, to encourage them to exert a sincere effort during lab investigations. I find this is accomplished by combining a completion grade with the plcu grade. As a result, a low plcu score, 4 out of 10 for example, will result in a 70% lab score as long as the student has been involved in the process. In the past, this is a typical grade for labs in which the student participated and appeared to complete the lab, but the data were poorly evaluated or collected. However, I do not use this for investigations that last several class periods and require a more formal write-up.



This week's article is contributed by Dave Smith. Dave is a graduate of Wheaton College in Wheaton, Illinois. He has been a high school physics teacher for 24 years. Dave is currently teaching Regular Physics and Honors Physics at Glenbrook South High School in Glenview, IL, where he has served since 1997.


Dave is sharing three examples of his many Post-Lab Check Ups.  The three examples are available for downloading and inspection:

• Waves at Boundaries
• Horizontally Thrown Projectiles
• Investigating Circuits

If you are a science teacher and have something to share, consider contacting the Lab Blab blog coordinator.  Your ideas could soon appear here on the Lab Blab and Other Gab pages.

Confessions of a Coattail Curber

I can't believe I said it.  They can't believe I said it.  Once more, I let careless words slip out of my mouth.  Like a dagger in the heart, they hit two of my favorite students with such force that their mouths dropped at a rate of 9-10 g's. How could I have been so insensitive? It took only five seconds; but in those five seconds I dashed Riley's and Ellen's hopes and dreams of another good lab. Seeing a group of six students crowded around a single table with only one set of equipment, I placed a molecular model kit on a separate table and said, "Riley and Ellen, let's have you come over here and work together."

Riley and Ellen's mouths opened wide.  It was as though I had broken the news that their best friend had died. Their faces immediately saddened, their postures changed and they even but-Mr-H-ed me. I've been teaching long enough to know that one! "But Mr. H, ..."  This but-Mr-H was noticeably different. There was a distinct trace of lowering intensity from the m-sound to the ch-sound accompanied by a little quivering along the way. This was a clear sign that I had crossed the line and they were VERY upset. Time seemed to stand still as they looked at me, looked at each other, looked at Lonnie, picked up their lab notebooks and slowly walk to the other lab table to work alone on their lab. It was at that point that I realized the dark truth about myself.  I am a coattail curber. 

There is six month's worth of evidence that shows that Riley and Ellen invariably gravitate to Lonnie's lab table.  All overt efforts on my part to vary the groups and to provide different partners and different experiences for students in labs are ultimately foiled by this sort of gravitation between Lonnie and Riley and Ellen.  The nature of this attraction seems to be related to Lonnie's tendency to understand the lab environment. Riley and Ellen's need to be partnered with a student who understands the purpose and is able to plot out a procedure, manipulate the equipment, collect the data, perform the calculations and reason towards a conclusion. As far as Riley and Ellen are concerned, their association with Lonnie is a match made in heaven. As for Lonnie, Riley and Ellen are among the nicest two students you could ever meet. A little bit of nice will go a long way towards providing a lot of helpin'.

It could be said that Riley and Ellen ride the coattails of Lonnie.  Their success in lab is largely due to the coattail effect. Coattail effect. A phrase borrowed from politics which Wikipedia describes as "a generic phrase for anyone that hangs onto another person as they forge ahead, without effort from the hanger-on." For certain, Riley and Ellen are hanging onto Lonnie as he forges ahead. The Free Dictionary describes the coattail effect this way: "to use your connection with someone successful to achieve success yourself." For certain, Riley and Ellen are successful in lab insofar as Lonnie is successful in lab.  But the most vivid description of a coattailer comes from The Urban Dictionary: "To sponge, mooch, free load, skate by, or do absolutely nothing but watch while somebody else does all the work and still somehow try to take at least partial credit for something you had no hand in."  When six students crowd around a single set of material at a lab table, there are going to be several students who do nothing but watch while somebody else does all the work.  And you can bet these students are going to take at least partial credit for something they had no hand in.  In suggesting that Riley and Ellen separate from Lonnie and the other three members at the lab table, I was preventing the coattail effect.  I was being a coattail curber.

Now I assure you that I meant no harm on that fateful Wednesday morning. My intentions were entirely innocent.  In fact, I actually intended to do good towards Riley and Ellen and the other members at the table.  It was not my intent to curb anything.  I simply wanted to promote increased engagement in the lab activity. My logic was simple: as the ratio of the quantity of hands to the quantity of lab sets is decreased, the level of engagement increases and the amount of learning increases. My formula for success was that the smaller the group size, the greater the engagement and the more profitable the lab experience.  So I was simply migrating from table to table in an effort to reduce the group sizes to two students.  But in doing so, I was curbing the ability of many students to achieve success on this lab by means of the coattail effect.  I was a coattail curber.

When I was in high school, I played basketball on the school team.  During nearly every practice there was a moment when the coach blew the whistle and shouted "Free Throws."  We all knew what to do.  The coach did not need to say anything else.  We all got a ball, paired up and went to one of the eight baskets around the gym to practice our free throws.  The formula for optimizing this experience was simple: two players, one set of equipment. The smaller the group size at every basket, the more beneficial the activity. If your free throw partner was ill or injured, you didn't triple up with two other teammates; rather you considered yourself fortunate to have a basket to yourself at which you would get more free throw practice. In my four years of playing high school basketball, I never witnessed six players congregating at a single basket, each waiting their turn to shoot free throws while there were empty baskets around the gym. This was just not a sensible way to occupy the time. And never once did the entire team crowd around the best free throw shooters basket and watch him shoot free throws for 10 minutes, considering each success of his as being their own. That would be ludicrous.

 In making an effort on that Wednesday morning to reduce the size of lab groups, I was exercising free throw practice logic.  Two students, one set of equipment, an optimized experience. Just two weeks earlier, I had done a Young's Experiment Lab in one of my physics classes.  I had one laser, one slide with a double slit, one screen and 25 students. That's 25 students using a single set of equipment.  I enjoyed watching 8-10 students cooperate (and at times, argue) as they attempted to collect data to determine the wavelength of light. But what I didn't enjoy is watching the inactivity of a dozen or more students as they sat unengaged on the side of the room as a spectator. At first, they were humored by the feud over which of the little red dots on the screen to use for measuring y. And many of them were quite entertained as several students argued about how much sag to allow in the measuring tape s they measured the distance from the screen to the double slit.  But soon they zoned out and turned into Delilahs.  Engagement turned into spectatorship and the coattailers quickly lined the sidelines. So when I made the effort to break up the groups of four and six into smaller groups of two students, I was simply attempting to optimize the experience for my students.  It was using free throw practice logic.

After some further resistance, Riley and Ellen crowded around their own set of molecular models and worked on the lab together as a twosome.  I periodically circulated through the lab over the course of the next 30 minutes.  Each time I passed by Riley and Ellen's station, I observed 100% engagement.  I also observed science talk, lots of thinking, growing confidence and great progress.  As the period ended, Riley and Ellen returned to the front of the room with a smile on their face and a sense of pride in their hearts.  Riley commented, "Mr. H, aren't you proud of us?  Ellen and I finished the lab on our own. Aren't you proud of us?"  I winked, smiled and affirmed,  "I knew you could do it. I AM proud of you."

As Riley and Ellen left the room that day, I thought to myself:  I'm proud to be a coattail curber. If I want my students engaged in doing science, I will have to provide environments which are conducive to engagement. And one aspect of such an engaging environment is group size.  While there may be occasions for which larger groups offer more benefit than smaller groups, I've observed that engagement generally increases when free throw practice logic is applied to group size. Especially for those very passive students who generally "sponge, mooch, free load, skate by, or do absolutely nothing but watch while somebody else does all the work", minimizing group size goes a long way towards increasing their engagement.

So the first very practical means of salting the oats involves curbing the coattail effect by limiting the group size.  Next week we explore one teacher's strategy for encouraging engagement and investment in lab activities which has shown positive gains even in situations in which the group size is more than desired.


This week's article is written by Tom Henderson.

Salt the Oats

My friend was a pastor at a church.  He often referred to himself as an evangelist.  He really wasn't an evangelist, but he described evangelism as being his gift.  And he was right.  In a blink of an eye, he could turn a conversation about sports into a discussion of religion; and somehow you would never know that the topic had changed to religion until you were 10 minutes into the conversation.  His ability to subtly and naturally change the course of a conversation was amazing; and his ability to do it without offending even the most disinterested and resistive individual was equally amazing.  Regardless of where a person stood with respect to a religious belief, my friend had the uncanny ability to draw the person towards a serious discussion and consideration of matters of faith.

I often view my role in the classroom as being like that of an evangelist.  Many of my students are quite resistive to science or at least to some aspect of science.  As the instructor, one aspect of my role is to get as many as possible enthused about the topic, informed about its logic, and recognizing its value in answering questions.  My students are willing to sit in their seats and to be entertained and even educated by a well-planned science lesson. But when it comes time to being engaged in the act of doing science in a laboratory environment, so many quickly default to passivity. They adopt a sort of "science is cool for you, but I'm not really into it" attitude. Like my evangelist friend, I am faced with the challenge of getting the disinterested and the resistive to listen, to learn, to recognize the value of, and to ultimately embrace the practice of doing science.  For certain, enthusiasm, humor, energy, a repertoire of intriguing demonstrations, and a carefully crafted curriculum are among the ingredients to get the disinterested and the resistive to listen to a lesson and maybe give science a second look. But exactly how do I get these same couch potatoes to check their passivity at the door of the laboratory and to become actively engaged in scientific inquiry?

One day I asked my friend if he ever became frustrated by the disinterest and the resistance which others demonstrated towards his message.  I sensed that he was frequently victimized by the "you can lead a horse to water but can't make it drink" syndrome. Being curious, I asked him what he does when "he leads a horse to water but can't get it to drink."  His response was immediate: "I salt the oats." Salt the oats.  Of course! Thirsty horses will need to drink. And salty foods make horses thirsty (I think). What a brilliant idea! Salt the oats.

But what does that mean for a science teacher who is trying to get students interested and enthused about doing science?  How can I salt the oats and make students thirsty enough to drink? How can I entice Johnny and David and Sara and Julie and ... to become engaged in scientific inquiry during lab time?  In what way can I up the ante, change the medicine, modify the dosage, and salt the oats in order to get my students to drink up?

Over the next few weeks, our blog will turn its attention to a discussion of ways in which science teachers can salt the oats.  We will look at a variety of tactics which science teachers can use to get students more engaged during lab time.  In effect, the next several weeks of articles will be part of Lab Blab's Salt the Oats series.  Come back next week to learn how to salt the oats.


This week's article is contributed by Tom Henderson. Tom is the author of The Physics Classroom website.  He is a graduate of the University of Illinois in Champaign-Urbana, Illinois. He has been a high school physics teacher since 1989. Tom currently teaches Honors ChemPhys (Physics portion) and Honors Chemistry at Glenbrook South High School in Glenview, IL, where he has taught since 1989.