A new study from Stanford University might help explain why previous studies have shown that black students are expelled at a significantly higher rate than their white counterparts.

The problems start early, after just a second rule infraction.

“We have shown experimentally, for the first time, that teacher responses can contribute to racial disparities in discipline,” the researchers said in a paper published in the journal Psychological Science. “In fact, teacher responses may even help to drive racial differences in student behavior — differential treatment by teachers, to some extent, may inspire repeated misbehavior by black students.”

In what researchers called the “black-escalation effect,” teachers were shown records of kids with either stereotypical black names (Deshawn or Darnell) or stereotypical white names (Greg or Jake) and asked what disciplinary steps should be taken after certain infractions.

While the response to the first infraction was the same across both races, after the second rule infraction, teachers pushed for more punishment for the black students than the white students.

“It’s not that these are racist people, it’s just that we all are exposed to stereotypes in the world,” said Jason Okonufua, the study’s lead researcher.

“Most social relationships entail repeated encounters,” Okonofua continued. “Interactions between police officers and civilians, between employers and employees, between prison guards and prisoners all may be subject to the sort of stereotype escalation effect we have identified in our research.”

While the researchers have suggested that an intervention program be implemented for teachers to point out their biases, they also acknowledge that the issue runs deeper than just a surface program.

“This is not a one-step thing you can do and be inoculated against implicit bias,” said Dennis Parker, director of the ACLU’s Racial Justice Program. “It requires monitoring and retraining and careful observation. But the first step is that acknowledging that implicit bias is an issue.”