Oh yep...studies have shown that teachers DO treat boys and girls differently throughout school. And yes, boys are treated "tougher" than girls are. As an elementary teacher myself, I try really hard to treat all of my students the same, but sadly, I am in the minority. I can say this from experience/observation of other teachers.
Also? I've noticed that teachers with boys tend to do better at treating them equally! I have had MANY parents request me for their son's teacher, because they perceive me to be "better" with boys. Maybe it's because I don't expect ANY of my students to "sit still and be quiet" 100% of the time! What 7 year old can do that? HECK; most adults can't do that! LOL!
If he likes the teachers, leave him there. That's what's important, as long as there is no obvious abuse. In the future, ask other parents as to which teachers "get" boys. They'll be able to give you names!