First yoiu shouldn't be taking weed to school. Let this event be a warning and a lesson.
Secondly the school is a government facility they have the right to search you as soon as you step onto school grounds for ANY reason. even if they dont like the color of your shirt.
If you take weed to school and get busted its your own fault, you smoke the ganja use common sense, no wonder stoners have the stereotype of stupid and burnt out.