Longman Dictionary of Contemporary English
middle school
noun
EXAMPLES FROM CORPUS
▪ Another letter from the middle school was about a visiting theatre group and asked for money as well as a tear-off slip.
▪ In middle school, your children would rather attend your execution than have you attend their field trip.
▪ Linda first saw Red at a middle school volleyball game.
▪ My own work on middle school teachers provides some support for this view.
▪ This does to, but in the back they all the covenant kids listed together, all the middle school kids.
Wiktionary
middle school
n. (context schools English) A school which crosses the traditional divide between primary school and secondary school
WordNet
middle school
n. a school for students intermediate between elementary school and college; usually grades 9 to 12 [syn: secondary school, lyceum, lycee, Gymnasium]
Wikipedia
Middle school
A middle school (also known as intermediate school or junior high school) is a school for students older than elementary school, but not yet in high school. The ages covered varies between, and sometimes within, countries.