Among the less-than-ideal behaviors you might encounter during the teen years is the problem of sneaking out. The curfew you set for your teen means she might not get to take part in activities her friends are taking part in -- and since her friendships are some of a teen's most important relationships, she may choose to defy you in favor of hanging with friends. It's tough to monitor your teen when you're asleep, so you'll have to rely on some outside help.
Remind everyone in the home -- including your teen -- of the rules about leaving the house. Talking with your teen about your expectations and the consequences of not following the rules is an important component of teen monitoring, reminds the Centers for Disease Control and Prevention. Let younger and older siblings alike know that sneaking out can be dangerous, since it means other family members won't know where that person is and can't step in to help. Ask siblings and family members with rooms near the teen's -- or who share rooms with the teen -- to tell you right away when they hear something suspicious.
Place a baby monitor or other listening device in her room, and then put the other one in your room. If you're a light sleeper, this might help you hear when your teen is leaving the room or opening a door or window.
Install an alarm system on your windows and doors. Set the alarm to go off when any doors or windows are opened in the middle of the night.
Set up a tracking system on your teen's phone. Since your teen will probably need her phone to call friends when she sneaks out, this can help you find out where she's gone. A number of apps will also allow you to see the phone calls and texts your teen is receiving, helping you stay on top of all sorts of unwanted behaviors. (See link in Resources)