I was confirmed in 10th grade, but our diocese switched a while ago to “restore the order” of the sacraments. If you think about it, adult converts are confirmed before they are admitted to communion. The Eastern churches confirm right after baptism.
I don't know, i like 8th grade for Confirmation. it's about the gifts of the Holy Spirit; 8th grade is a good time to talk about that, chastity being a good topic of conversation as they are ready to head off to HS etc. it is a nice way to strengthen them, at a time when kids really seem to need it.
At our school, we were all confirmed in 6th grade.