All my schooling was co-educational. I changed schools during my first year in junior school (aged 7). From what I remember of infants’, girls were in trouble more often than boys. It was a long time ago though and I might have just noticed more when a girl was in trouble – knowing it could so easily have been I.
In junior school, behaviour patterns might have been different (I tended join in with boys because “girly things” didn’t interest me) but disregard for the rules seemed to be about equal for both sexes. Girls tended to be allowed more leeway, especially by male teachers, but female teachers didn’t reciprocate in the case of boys so, overall, boys would appear to misbehave more.
In secondary school, as I’ve said, we were all held to the same standards of behaviour and subject to the same rules. Some teachers were more likely than others to turn a blind eye occasionally but I can’t say I noticed any sex discrimination there.