Even people who work with students probably don’t realize just how much time kids spend online. The average American tween spends 4 hours and 44 minutes on their screens each day—and that is in addition to the time they spend on their devices doing schoolwork. For teenagers, that number goes up to 7 hours and 22 minutes. Students from lower socioeconomic backgrounds tend to spend still more time online than more privileged students do.

But just because tweens and teens spend seemingly endless hours online and have grown up with the internet, doesn’t mean they know how to use it responsibly.

While online, many students treat each other poorly. More than a third of students between the ages of 12 and 17 have been bullied online. Nearly a quarter of students admit to saying or doing something cruel online. In addition to hurting each other directly, students often engage in digital self-harm or expose themselves to the mistreatment of strangers: 15% of teens have shared explicit pictures of themselves to people they’ve never met. More than three-fifths of teens who have sent nude pictures report feeling pressured to do so. All these behaviors can have lasting ill effects on a student’s mental health and increase the risk of suicidal thoughts or actions.

With students confronting so many hazards while on their devices, districts looking to create a safe and respectful community for all students must focus their efforts on encouraging—and enforcing—good behavior online. That is, they need to teach students to see themselves as digital citizens.