In a primary school, boys are five times more likely to be told off than girls, even though they are just as likely to misbehave, according to a new study.
The bad boys are also less likely to be praised or picked to answer a question, despite raising their hands just as often as girls.
The study, led by Dr Jeremy Swinson, an honorary lecturer in educational psychology at Liverpool John Moores University, stated that the 'prejudiced' views of some teachers could be damaging boys' self-belief, causing them to do badly at school.
"Teachers assume that the boys are more badly behaved, possibly because the sort of bad behaviour they engage in is likely to be louder," the Telegraph quoted Swinson, as saying.
"They are slightly more prone to shouting out in lessons but these differences are quite small. Teachers tend to be more cautious about boys because they perceive them to be potentially more trouble. I don't think they are.
"The other issue, particularly at secondary school level, may be that boys tend to be bigger and therefore teachers tend to become slightly more defensive," Swinson added.
Swinson followed behaviour in classes at two primary schools in Liverpool, and found that there was a "common belief" that boys were more easily distracted and prone to misbehave, but it was not borne out by the research.
He said that girls were just as likely to step out of line, although he acknowledged that their pattern of misbehaviour meant they were less likely to be spotted.
The study found that boys tended to "shout across the classroom", while girls broke the rules by reading under the desk or passing notes between friends.
When girls become bored in lessons, they are also more likely to "switch off", while boys make noise as their attention wanders.
Swinson said that this "prejudice" could explain why girls get better exam results than boys. "Perhaps some boys get disenchanted with lessons because they are being told off too much," he said.
The researcher said that teachers should deliberately praise children on either side of the offending pupil to provide a subtle message that misbehaviour has been noticed.