When it comes to tests and exams, girls generally do better than boys.
Girls beat boys in the new grammar, punctuation and spelling test in this year's Key Stage 2 Sats in England.
And in GCSEs in England, Wales and Northern Ireland, girls got more A* and A grades.
No one's quite sure why girls do better but researchers are hoping to find out.
Bonny Hartley from Plymouth University said: "Children believe that girls behave and perform better than boys, and they also think that adults think this too."
"Boys perform less well when they're aware of these expectations," she said.
Some people think there's a lack of male teachers or that classes are just not interactive enough for boys.