you should find somewhere you can get clean piss (some goody good at school who you can pay like 10 bucks) and just do that.

or just chill with it for awhile till you're 18, then light a joint, blow it in his face, and tell him to go fuck himself.

or you could just fail another drug test, get fired, and start selling weed to make your ca$h. and when he asks where you're getting all your money, just tell him you're stealing it from his wallet because he won't let you get a job