Happy New (School) Year

Why is it that I can't seem to get "excited" about the new school year? I keep dreading my new class, even though there are several children that I already know and like. It's only a very small minority that I'm concerned about, yet they monopolize my thoughts and make me anxious. Like three or four bad apples in the bunch. Unfortunately, I can't just chuck them out. Or can I???.....