Son is just coming up for ten (yr5).
Over the last few weeks he is detaching from school saying teachers not being fair so much so teacher asked if everything is ok!
Have talked about it & he says that same people get picked for stuff, his class is 'full of idiots' general moody/misery 
He is in a 'challenging' class (2/3rd boys) many confident kids. He is competent and quietly confident but feels badly behaved kids get rewarded!
Any advice/perspective of others experience would be good 