Generally middle schools are grades 6-8, junior highs 7-9 (or 6-9). They aren't usually the same thing.
If you have an early birthday, it wouldn't be unheard of to be 14 in grade 8 by now.
Off-topic: the whole "middle school" issue was discussed more in this thread:
http://forums.greekchat.com/gcforums...threadid=47763