Were you ever the teacher's pet? Or did you just sit behind the teacher's pet and roll your eyes from time to time?

A newly published paper suggests that personality similarity affects teachers' estimation of student achievement. That is, how much you are like your teacher contributes to his or her feelings about you — and your abilities.

"Astonishingly, little is known about the formation of teacher judgments and therefore about the biases in judgments," says Tobias Rausch, an author of the study and a research scientist at the Otto-Friedrich-Universität Bamberg in Germany. "However, research tells us that teacher judgments often are not accurate."

This study looked at a group of 93 teachers and 294 students in eighth grade in Germany. Everyone took a short test to establish basic features of their personalities: extraversion, agreeableness and the like.

They gave the students reading and math tests too, sharing the test items with the teachers. Then they asked the teachers two questions: How good is this student compared to an average eighth grader? How well will this student do on this test?

In other words, the first question asked the teacher to give a global judgment; the second asked for a task-specific judgment.

The study found that when teachers and students were peas in a pod, the teachers overestimated the students' general abilities. Conversely, students who were dissimilar from their teachers were judged less positively.

But when the judgment was grounded to a specific test, the effect disappeared.

This finding is maybe not that surprising. But it's important for two reasons.

First, there's concern that teacher bias of many kinds may unfairly hold back groups of students.

For example, a recent study from Israel showed that teachers gave girls lower grades on math tests when they knew their gender. And lots of researchers have looked at the importance of having teachers who share the racial and socio-economic backgrounds of their students.

If teachers give students who are similar to them better grades, or even just maintain higher expectations of those students, what does that do for the students who don't look or act like their teachers?

Second, as Rausch, the co-author, points out, this study points to the importance of balancing teachers' "holistic" evaluations with standardized assessments, or at least assessments that aren't graded by a student's own teacher.

Rausch also says it might be a good idea to spend more time training teachers to notice their biases. "The best way to control for is probably raising teachers' awareness concerning the way they assess their students' competencies and their awareness concerning typical judgment biases and tendencies," he says. Human judgment, after all, is only human. Copyright 2019 NPR. To see more, visit https://www.npr.org.