Summarize:

Make sure the benefits will outweigh the consequences of skipping class. Know the rules at your middle school. Each school has a different absentee policy, but you will want to know what is going to happen if you skip a class before you decide to leave. Beyond the penalty dealt by your middle school, there are effects on your likelihood of success as a student if you are a habitual skipper. It's possible you will get detention and have to spend more time at school. Will you be allowed to take a test later if you skip a class to miss a test? What are the consequences of turning homework in late? What will happen if your parents find out? Will this just lead to longer stints of boredom and less opportunity to hang out with friends because you're grounded? Students who skip more than 10 days of school in a year are 20% less likely to get a high school diploma and 25% less likely to go to college. Those who do skip often feel like they are behind in their learning. Understand the truancy laws. Public schools require attendance. If you are absent and do not have a reason which falls under excused absences, you will be marked as truant. This applies even if you get a note from your parents excusing you if the excuse does not qualify to avoid truancy. Excused absences are usually related to illnesses, a death in the family, or religious observances. Some excuses that could work are telling them you got a migraine headache and needed some quiet, you suddenly feel nauseated, you needed to call your parents. Extended absences for health reasons will often require a doctor's note. Rather than just wandering in the halls and getting caught, think of different ways you can get out of class without getting into trouble. Make sure you know what you want to do and how you want to do it before the class period you want to skip. Come up with a list of options which may work, then choose the one you think is best. Consider going to class and asking to be released by the teacher to see the counselor, go to the bathroom, spend some time in the library, or call home. Check with the counselor and set an appointment for later in the day during the class you would like to skip. If you don't think the teacher will let you out of class, choose a place you can hide between classes, maybe even go by these places between other class periods to see if they look like good hiding places.
Weigh the consequences. Have a good excuse. Plan in advance.