My Take on Assessment

Student assessment (—we used to call it evaluation; before that it was testing—) is ever-changing.

There are many ways that assessment can be done well. What works for one teacher in a particular setting, with a particular student group, operating under a particular set of school-administration rules may not work for everyone. That’s okay. I propose to tell you what worked for me, in an all-boys independent school.

Back in the day, I gave quizzes and unit tests; students completed homework; they submitted lab reports. Over the years, I streamlined this approach—for everyone’s benefit, I think:

1. I never graded or collected homework. I saw this as a “do it don’t do it” kind of thing. It never took long for students—and their parents—to see a positive correlation between effective at-home practice and real learning.
2. I got rid of formal lab reports. I—and my students—saw them as pointless. Formal lab reports were simply too big a cost in terms of time¹, with too little benefit in terms of learning. They were a whole lot of busywork.² I made the following changes: Every practical activity began with a pre-lab class discussion, followed by pre-lab questions (as appropriate), and post-lab questions. Post-lab questions included the writing of an abstract³, which students found challenging; inclusion of a data/observation table; graphs if appropriate; calculations (if appropriate); and, or course, analysis. This allowed students to spent time on things that mattered. Further, my unit tests (assessments), described below, drew heavily from labs and class demonstrations, incentivizing students to pay close attention to this most-important aspect of the class.
3. As a result of a change in school policy, my mid-unit quizzes were pretty much eliminated. These morphed into short quizzes (5 points maximum) that were taken—open notebook—immediately after a lesson, after having been announced at the start of class. Quizzes of this type “helped” students to take good notes and to ask plenty of questions. Additionally, each student immediately marked his own paper before handing it in to have the grade recorded.⁴ This was mutually beneficial: I didn’t have to mark the quizzes; students had immediate feedback on the nature of their mistakes. I think that this is called “Assessment for Learning”, or something like that.
4. Again, owing to a change in school policy that mandated that tests be no longer than 45 minutes, unit tests were split into two parts.

 

Part 1 was an extensive set of take-home questions—essentially a review sheet that counted 60%. I called it a “Collaborative Assignment”, inviting students to work together, using their textbook and class resources. In spite of my entreaties, I’m pretty sure that some students availed themselves of tutorial assistance and the internet—what could I do?⁵ Owing to the length of this assignment, it took a lot of time and effort, but was an effective vehicle for study. Students reported that it increased their learning. Many, of their own volition, chose to complete as much of the assignment independently before consulting their peers. This made me happy.

An unintended, human nature-related consequence of a Collaborative Assignment is that, often, many students would submit similar—incorrect—answers. I hypothesize that this occurred when a reasonably well-respected student—or the smartest guy in the class—put forth a decent-looking, yet not-completely-correct response. Unthinking, his classmates accepted it—and made it their own. I tried many times to make students aware of the need to think critically, regardless of the information’s source. I see this as a corollary to one believing everything that he or she sees on TV.

Some students chose to complete the Collaborative Assignment alone. While I respected this, it deprived them of the opportunity to talk about chemistry—and maybe even learn more chemistry.

 

Part 2 was a in-class, all multiple-choice test.⁶ Students had access to our Chemistry Data Sheet, and a calculator (when required): no notes, no “study sheet”, no nothing. Over a multi-decade teaching career, I learned how to write high-end multiple-choice questions that reveal understanding, not memorization. Here are several “random” (as the students say) examples, taken from Grade 11 and AP Chemistry. Questions 3–5 are bounded by dashed lines; they reference a class demonstration.

1. Imagine that you are a chemistry teacher with a limited budget. If you have only 50 mL graduated cylinders, graduated every mL, which of the following would be the best, most cost-effective electronic balance required to determine the density of water to the highest level of precision? 

(density of water = 1.00 g/mL)

                  (a) balance records to 1 g (cheap! cheap!  . . . Wal Mart here I come!!)    

                  (b) balance records to 0.1 g  (not too badly priced)

                  (c) balance records to 0.01 g  (start playing the guitar in a subway station)

                  (d) balance records to 0.001 g.  (mortgage the school)

 

2. Which of the following are false regarding the carbon-hydrogen combustion analyzer?

                  I.  the sample to be analyzed must be carefully massed before analysis

                  II.  all of the O in the sample is converted to O in H₂O

III.  the mass of the water absorber and of the CO₂ absorber must be recorded before and after the experiment

IV.  a carefully measured amount of O₂ must be added.

V.  the water absorber must be situated immediately after the furnace in which the sample is combusted.

                  a) I, III, V                 (b)  II, IV                  (c) II, IV, V                    (d) IV, V                               (e) II, V

 

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Questions #3-5 refer to the demonstration in which CO₂(g) was added to about 30 millilitres of concentrated sodium hydroxide solution, NaOH(aq), in a 2-L soda bottle, which was then sealed and shaken. (The CO₂(g) was produced by reacting (excess) HCl(aq) with solid baking soda, NaHCO₃.)

 

3. In which manner did we collect the CO₂(g) in the pop bottle?

                  (Air is approximately 29 g•mol^–1; HOH(l) is 18.0 g•mol^–1)

 

                  I.               by downward displacement of water

                  II.              by upward displacement of water           

III.            by upward displacement of air

                  IV.            by downward displacement of air

                  (a) I only                                   (b)  II only              (c)  III only                               (d) IV only             

                  (e) I, III                                       (ab) II, IV                (ac) any of the above would’ve worked

 

4. What reaction/process occurred?

                  (The following chemical equations may not be balanced—that’s okay)

                  a) NaOH(aq)  +  CO2(g)  →  Na₂CO₃(aq)  +  HOH(g)

                  b) NaOH(aq)  +  CO2(g)  →  Na₂CO₃(aq)  +  HOH(l)

                  c) NaOH(aq)  +  CO₂(g)  → Na₂O(aq)  +  CO₂(aq)

                  d) NaOH(aq)  +  CO₂(g)  →  Na₂O(aq)  +  CO₂(g)

                  e) NaOH(aq)  +  CO₂(g)  →  Na₂O(aq)  +  CH₄(aq)

                  ab) NaOH(aq)  +  CO₂(g)  →  Na₂O(aq)  +  CH₄(g)

                  ac) No reaction occurred; the CO₂(g) simply dissolved in the aqueous solution of NaOH

                 

5. What was observed after the demonstration; what did this tell us?

                  I.               the volume of the bottle decreased; CO₂ reacts with NaOH(aq)

                  II.              the volume of the bottle decreased; CO₂ dissolves in NaOH(aq)

                  III.            the volume of the bottle increased; CO₂ reacts with NaOH(aq)

                  IV.            the volume of the bottle increased; CO₂ dissolves in NaOH(aq)

                  V.              the volume of the bottle decreased; NaOH is deliquescent        

                  VI.            the volume of the bottle increased; NaOH is deliquescent         

                 

                  a) I           b) II                            c) III                           d) IV                          e) V                           ab) VI    

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6. Which of the following statements concerning bond energies is/are true?

I.               ∆H_r = Σ bond energy of bonds broken — Σ bond energy of bonds formed

II.              tabulated bond energy values are highly accurate

III.            ∆H_r = Σ bond energy of bonds formed — Σ bond energy of bonds broken

IV.            tabulated bond dissociation energy values are typically average values

V.              a table of bond dissociation energy values can be used to calculate the ∆H_r for many reactions

(a) I, II, V                 (b) II, III, V                                (c) I, IV, V                                  (d) I, IV                     (e) I, II, IV

 

7. Which of the following is/are true concerning a coffee cup calorimeter?

                                    I.    it is a constant pressure calorimeter

                                    II.   it is a constant volume calorimeter

                                    III.  it “steals” some energy from an exothermic reaction

          IV.  each coffee cup calorimeter will have a unique heat capacity value expressed in J∙^°C^–1

                  V.   each coffee cup calorimeter will have a unique heat capacity value, expressed in J∙g^–1∙^°C^–1

                                   VI.  when we carry out calculations, we consider the calorimeter to be the system

                                   VII. the heat capacity of the calorimeter is taken as 4.0 J∙g^–1∙^°C^–1

 

a)  I, III, VI                                b) I, III, VI, VII                         c) II, III, V                d)   II, V, VII                             

e) I, III, IV                                 ab) II, VI                                    ac) II, IV, VII          ad) I, IV, VII

 

 

Not all of my m/c questions were this challenging; many were run-of-the-mill. That said, student performance was typically lower on Part 2, but the combined result was usually decent. While I was fortunate to dodge parental complaints regarding grades—maybe the Zoom-based Parent-Teacher conferences helped—I was ready to say something like: “Hmmm . . . help me understand why your son scored 95% on the collaborative portion, but only 61% when he flew solo?”

So that was the assessment strategy I used for my final few years of classroom teaching. I hope that this provides you with food for thought.