For many families, the start of school is a busy, exciting time of year. For some students, though, returning to school also means bullying, and the feelings of anxiety, sadness and loneliness bullying can cause.

Up to 20% of students 12-18 experience bullying in the U.S. each year, according to StopBullying.gov, which is a resource managed by the Department of Health and Human Resources dedicated to providing information about bullying.

Bullying is a form of aggression, where one or more children repeatedly and intentionally intimidate, harass or harm a victim perceived to be less powerful. While bullying once was considered a childhood rite of passage, it is now recognized as a serious problem that can affect a child's physical health, emotional well-being and academic performance.

Bullying can take many forms, including:

• Physical: This type of bullying includes hitting, tripping and kicking, as well as destruction of a child's property.

• Verbal: Verbal bullying includes teasing, name-calling, taunting and making inappropriate sexual comments.

• Psychological or social: This type of bullying involves spreading rumors about a child, embarrassing him or her in public, or excluding him or her from a group.

• Electronic: Cyberbullying involves threatening or harming others through the use of email, websites, social media platforms, text messages, or videos and photos shared electronically.

Talking about bullying before it happens sets the stage for preventing and addressing the problem. If your child is being bullied, he or she might remain quiet out of fear, shame or embarrassment. Warning signs may be vague, and some may mimic mental health issues. If you suspect or know your child is being bullied, it's important to be proactive.