Classroom Bias: Before you say “I don’t do that.” Consider this…

Teachers regardless of your superhuman powers commit a grave mistake.

Let me explain…


Jimmy and Sarah have to take a math test.  The math test consists of 30 multiple choice questions.  On the first half of the test Jimmy got 7 of 15 questions right and Sarah got 14 of 15 questions correct.

On the second half of the test, Jimmy does much better.  He gets 14/15 questions right.  Sarah on the other hand only gets 7 of 15 correct.  Logically, these two students have mastered the same amount of content.

But we are not as rational as we believe.  Here’s what I mean…

When they get the tests back, Sarah’s comments are:

“Excellent job Sarah.  I’m sorry that you misunderstood the last few questions.  Let’s talk after class about how you can make up the grade.”

Jimmy’s comments on the other hand say something like this:

“Jimmy good recovery on the last part of the test.  Please study more next time.”

What just happened?

What’s wrong with this teacher?

How could she so badly misjudge the situation?

Here’s why….

As we have discussed before, your brain is a scrooge when it comes to detail.  We rely on simple and efficient thought processes to get the job done.  Human thought, like any complex process is a tradeoff between speed and accuracy.  We rely on heuristics or rules of thumb.

(If you think motivation and engaging students is important then you might want to check out the Engagement Checklist because it is a surefire way to engage students.)


It gets worse…

The rules of thumb apply to our judgements of other people.  This includes our students.

Quick question:

Which do you think is more likely to happen?

a. Being attacked by a shark

b. Being struck by lightning

Choose one…

If you chose shark attack, congratulations, your human and fell victim to a shortcut. 

Here’s the kicker:

Once we perceive someone a certain way (Sarah = math phenom and Jimmy = slacker) it is nearly impossible to change our mind.  This is called the primacy effect.

What happens after a first impression does jack squat to sway your opinion.

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It gets worse…

Jimmy is not a very attractive boy and is shy.  Chances are you will already tend to think he is unintelligent.

This is called the Halo effect and it swings both ways.  The halo effect is a specific type of confirmation bias, wherein positive feelings in one area cause ambiguous or neutral traits to be viewed positively.

If the observer likes one aspect of something, they will have a positive predisposition toward everything about it. If the observer dislikes one aspect of something, they will have a negative predisposition toward everything about it.

If Sarah is pretty and outgoing, you will unconsciously determine or at least suspect that she is intelligent as well.

Before you say “I don’t do that.”  Consider this…

In 1966 a monumental study was undertaken that is not as well publicized as it should be today. Before the school year began, teachers were told that an average of 20% of the children had unusual potential for intellectual gains over the course of the year. The researchers claimed that these students had done abnormally well on an intelligence test and were going to be “star” students.


They cautioned the teachers to understand that the differences in the “star” students and “regular” students might not appear at first, but be patient because their intelligence will bloom. After 8 months, these students were tested again. The “unusual children” showed significantly greater gains in IQ that did the “regular” children.[i]

No big deal right?

Except, the “unusual children” were selected at random. They had not shown anything “unusual” in the beginning of the year test. Yet, they significantly outperformed the “regular” children. Why?

It’s called the Pygmalion Effect. It happens when people are labeled as high performers or low performers.

When you are labeled a high performer, people set higher expectations, engage in more supportive behaviors, communicate more warmly, and provide them with more feedback.

“In the first grade, the bloomer’s out-gained the control students by about 15 IQ points; in second grade the difference was about 10 points. In both grades, the control students gained IQ points—but such gains were not even close to those gained by the bloomers.[ii]

If you teach at a school with a significant high risk population (as I have my entire teaching career) you should take caution because,

“… some large self-fulfilling prophecies have been found especially regarding members of some at-risk groups.”[iii]

This happens in other situations as well, not just in the classroom. Brian McNatt conducted a meta-analysis of 17 studies on the subject of self fulfilling prophecies in management situations.

His conclusion was:

“Performance measures in these studies included exam scores, performance appraisals, and physical output. Results indicate that Pygmalion effects can be fairly strong within some management contexts.”[iv]

Here’s the interesting part….

Before watching a video on a fourth grade student, regular and special education teachers were told that the student was either emotionally disturbed, possessing a learning disorder, mentally retarded, or “normal”. The teachers then completed referral forms based on the child’s behavior.

The teachers who were told the student was emotionally disturbed said the behavior was that of someone mentally disturbed.

The teachers who were told the student had a learning disorder thought the behavior was evidence of a learning disorder

The teachers who believed the student was mentally retarded thought the behavior was evidence of being mentally retarded.

However, the student was a “normal” 4th grade student who had never been diagnosed with anything.

According to the authors of the study:

Results indicated that teachers hold negative expectancies toward children categorized even when confronted with normal behavior, behavior inconsistent with the stated label… this bias is sufficient to cause teachers to misinterpret actual child behavior, resulting in a halo effect…  label of mentally retarded generated a greater degree of negative bias than did the labels learning disabled or emotionally disturbed

Think for a moment about what that means.

Even though the student was never diagnosed, teachers said they observed behaviors that were consistent with being mentally retarded.

Daniel Kahneman, a famous psychologist and Nobel Prize winner, writes that he too struggled with the halo effect:

“The first question I scored had a disproportionate effect on the overall grade.  The mechanism was simple:  if I had given a high score to the first essay, I gave the student the benefit of the doubt whenever I encountered a vague or ambiguous statement later on…. If a student had written two essays one strong and one weak, I would end up with different final grades depending on which essay I read first”

Now here comes the good part…

We can combat these biases by being proactive.

  1. Grade anonymously.  It becomes tempting to give some students the benefit of the doubt.  Grade anonymously whenever possible.
  2. Use written rubrics. It makes it much more difficult to be swayed if you use a rubric.
  3. Grade tests question by question rather than student by student.

To combat these biases, you basically have to make sure the assignment is consciously separated from the student who did it.  Also, hopefully by understanding these biases, you will begin to combat them in your own way.

Any more suggestions?


PS – If you think motivation and engaging students is important then you might want to check out the Engagement Checklist because it is a surefire way to engage students.


[i] Rosenthal, R., & Jacobson, L. (1966). Teachers’ Expectancies: Determinants Of Pupils’ Iq Gains. Psychological Reports, 115-118.

[ii] Jussim, L., & Harber, K. (2005). Teacher Expectations And Self-Fulfilling Prophecies: Knowns And Unknowns, Resolved And Unresolved Controversies. Personality and Social Psychology Review, 9(2), 131-155.

[iii] Ibid.

[iv] Mcnatt, D. (2000). Ancient Pygmalion joins contemporary management: A meta-analysis of the result. Journal of Applied Psychology, 85(2), 314-322.

This post was inspired by reading this book:

v Grant Halvorson, H (2015). No one understands you and what to do about it.

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  1. Extremely useful article! I truly appreciate the solutions to the problem. Being “efficient” has a new meaning for me now. Thank you so very much!

    Liked by 1 person

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