Describing Middle School in european grant application I completed my PhD in the US, and I am currently writing a grant application for a EU grant.  While I was a graduate student, I worked on a grant that had me in a middle school classroom (8th grade, so 12-13 year old students).  

What is the best, short way to describe this in my grant proposal? I don't want to waste a lot of space describing the specific age range of the students, if it can be avoided.  At the same time, I don't know if it will be clear what I mean if I write "8th grade classroom" or "middle school classroom".  Any ideas?
Describe it like you did here: 8th grade, and then in parenthesis put (ages 12-13) to remove any ambiguity. That will only cost you a couple of words, and no one can misunderstand.

To expand on @ORMapper commented, in Sweden middle school would be "mellanstadiet" which is grades 3-5, and the students are aged 9-11. So specify both what the gade was "called" and the age, and avoid descritors like "middle school"that can vary a lot by country.