When teachers place stereotypes on their students they are unaware of their actions. They believe that they do not place children in gender roles, but when they become aware of their actions, they are likely to change their attitudes that they too part in stereotypical actions. Peers place pressure on individuals to insist that they act as a group with the same behaviors as the group. For example, when a young boy is friends with a girl his boy peer group will place pressure on him to stop being friends with the girl and join their group. If the boy does not join his peer group he will be considered an outsider and not accepted by his peers.
Teachers place pressure on boys to excel in math and the physical sciences.
The boys then are motivated to succeed in order to gain a reward of appraisal by the teacher. There is less pressure placed on the girls because they are already expected to achieve. Boys are expected to be aggressive, independent, and clever. Girls are expected to have good behavior, show obedience, passivity. Boys will be boys and girls will be girls.