Summarize:

Each school sets its own rules on absences. Find out how many absences you have already, and what the consequences are for the next one. Even if you plan to sneak out without getting marked absence, there's always a chance you get caught. Figure out whether your worst case scenario is a minor mark on your record, or a serious consequence like suspension. If you can, choose a teacher that doesn't take roll every day. In general, you're more likely to get away with skipping a class if the teacher is relaxed and if you haven't been absent from it more than once or twice before. This is a limited resource; each teacher will only believe your excuses once or twice. But when it works, you have a consequence-free pass from the rest of class. Here are some ideas you can use:  Look antsy and say you have "bathroom problems." If you're female, say you are having a bad period or "female problems." Look upset and ask if you can talk to the school counselor. Deliberately leave a bag or other item in another room. Say you've lost it or left it in your gym locker, and claim there's something important inside (keys, wallet, etc — but don't actually abandon these). Leave your backpack in your locker so you look like someone walking to the bathroom, not someone trying to sneak out. If you are reasonably tall and go to a large school, you can try dressing in smart clothes and pretending to be an adult. This may save you from a staff member's passing glance, but don't expect it to save you if someone stops you. Tell your teacher you need to use the bathroom five or ten minutes before class ends. Even if the teacher doesn't let you leave, you have an excuse to rush out the door as soon as the bell rings. Your goal is to get as far as possible before passing period is over, while the halls are still full of people. Forging a hall pass could get you in serious trouble, depending on your school's policy. Holding an old hall pass or scribbled-on piece of paper the same color and size can be almost as good, depending on how strict the staff members are about checking. If staff members watch the exits during passing period, slip into a nearby bathroom or empty room and wait for the next class to start. Sneak out as soon as the exit is clear. If your school has very tight security, or if there's nowhere to hang out near your school, you could spend the whole class in a bathroom stall. You'd better have the best game ever on your phone for this to be worth it. In some places, truancy is a crime. Getting caught could mean serious punishment, so you've got to be relatively sneaky if you want to hang out with friends. Don't head straight to the pizza place all the kids go to after school, the mall, or the park across the street from school. Get away from the school, stay in quiet neighborhoods, and definitely stay away from places where your parents or their friends might see you. Walk directly away from the school when you leave the school grounds. Don't pass by any windows or chain link fences where a teacher can see you on the other side. Many schools phone your parents if you're marked absent from a class. It's up to you whether to own up and face the music, or whether to lie your way out of it. You know how your parents will react better than anyone, so use your judgement.  Use your knowledge of school policy to your advantage. If the school marks you absent after five minutes, claim you were just late coming from the bathroom or from the previous class. If one parent is much less strict than the other, bring up the subject when only the lenient parent is around.
Know your school's attendance policy. Choose which class to skip. Use an excuse when possible. Don't look like a truant student. Leave your previous class a few minutes early. Fake a hall pass. Slip out or find a hiding spot. Avoid obvious hang-outs. Prepare to face your parents.