It takes a little while to make "your rules" stick. Start with easy things. No pass, get ye back to class. This is easily enforceable, especially with the ms crowd. The other enforcable thing is to make complaints that can wait do just that - wait. If it's your friend with the nail, have har come back during har lunch or recess if they have one. I worked at a ms that didn't have recess, but did have a "free period" where the students were expected to read, catch up on homework, etc and I'd tell the students to return to ice their 3 day old bumps and re-bandaid their invisible boo boos then. 95% of the time they wouldn't return.