When your step disaster(no offence) is sleeping,have a couple friends grab him and say if he dosn't leave you alone,you'll put his head under the stairs all summer!

Tell you what...seriously,if he gets upset with your grades,tell him to (insert bad word) off or you will quit school.If he attempts to 'ground' you,walk out the door and flip him the bird on way.

Just ask and i'll give plenty more solutions to his 'authority'...He should be thankful your around at all..make it known to him that it could be much,much worse than just letting your grades slip.

(sorry,I can't stand to see anyone discouraged from productive behaviour)