Is it illegal to have Priority Mail Address Labels at school in the state of california?

well today me and my frined got suspended for having the labes(stickers) . the security insisted that we were going to use them for vndalims. I am a graffiti artist, but i dont do any illegal graffiti. the California Penal Code Section 594.2 does not mention any thing about having the labels...... so please hlp me out on this one