Take a good look at the person sitting next to you at work. They might have a lot more influence on your life than you give them credit for.

And it looks like this applies nowhere better than in the classroom.

A myriad of factors influence school achievement. Though not an exhaustive list, cognitive ability, teacher quality, and family backgrounds have much to do with it.

But there is one element that people might be less comfortable to talk about: the peer effect.

The presence of obedient and diligent students may positively influence outcomes for more disruptive students through knowledge spill-overs.

Conversely, having a classmate who is otherwise not interested in what the teacher has to say could affect their peers well into adulthood. Particularly if the teacher then has to devote more of their time to the student rather than teaching the class.

Knowing who is in your child’s classroom matters.

In New Zealand we continually obsess over the decile divide. Parents who bend over backwards to move their kids are sometimes alleged to be choosing on ‘social factors’ rather than ‘educational factors’.

Though choice on the latter may be misguided as current measures of school achievement do not account for student circumstances, the former may carry some weight. 

In their 2016 paper, Carrell, Hoekstra and Kuka show the long term consequences of having a disruptive classmate in elementary school. They looked at the impacts on test scores, college enrolment and completion, and on earnings.

Besides making his peers score worse on tests, the researchers found that one additional disruptive boy in a class of 25 would reduce his peers’ lifetime combined earnings by around US$100,000.

And they estimate that having four such classmates has roughly the same effect on peer future earnings as replacing an average teacher with one in the bottom 5 percent.

Though this is one study, the findings have implications for classroom composition. New Zealand tends to group students by not much else other than age, but these kinds of information could enhance teacher and student sorting.

And of course, for parents making school choices, it pays to have good information on what they value, whatever that may be.

So if it is the case that the same holds in the workplace: in future pursuits of employment skip the salary question and ask to meet the existing employees instead. It may just pay off.