In the US by the 8th grade, 48 percent of girls receive a mix of A and B grades compared to 31 percent of boys. More tellingly, Boys account for 71 percent of all school suspensions. The gap remains through high school and in college, with females representing nearly 60 percent of all college graduates.
“If you treat girls as the gold standards and boys as defective girls, that’s going to be demoralizing,” Thompson says. “What do elementary and junior high girls always say about boys their age? ‘You are so immature.’ If that’s the norm, then this system is just rigged against the boys.”
There's a wonderful bit in a 2013 Time article which illustrates that this predominant viewpoint is often indelibly coded on the (majority female) teaching staff, to the grave detriment of the male students:
https://ideas.time.com/2013/10/28/what-schools-can-do-to-hel...
//Peg Tyre’s The Trouble With Boys illustrates the point. She tells the story of a third-grader in Southern California named Justin who loved Star Wars, pirates, wars and weapons. An alarmed teacher summoned his parents to school to discuss a picture the 8-year-old had drawn of a sword fight — which included several decapitated heads. The teacher expressed “concern” about Justin’s “values.” The father, astonished by the teacher’s repugnance for a typical boy drawing, wondered if his son could ever win the approval of someone who had so little sympathy for the child’s imagination. ... If boys are constantly subject to disapproval for their interests and enthusiasms, they are likely to become disengaged and lag further behind//