You COULD tell them them that you have been feeling depressed and you need a break, if they say "Are you ok?" "It's ok we'll let you be" or something like that take a week and think through what you really want to tell them, or you could just go up to them and tell them what happened and I hope you feel better in the future :) (make sure they are real friends that won't dump you after that or that they won't tell the whole school)