If your teen's teachers have let you know that he's rude and obnoxious at school, you are probably upset and embarrassed. This type of behavior is usually normal in teens and is their way of asserting and standing up for themselves, notes James, Lehman, MSW, with the Empowering Parents website. While the school will probably take action for his behavior, reinforcing the rules about being rude and obnoxious at home can help your child refrain next time.