Translation:The pupils of the school loved the performance.
No. "Forestillingen" means "Performance", as in a theatre, or "vision or idea". "Præstation" means "achievement". http://da.bab.la/ordbog/dansk-engelsk/forestilling http://da.bab.la/ordbog/dansk-engelsk/praestation
ScolENs elever = THE pupils of THE school? But elever is not eleverne, so it is not definite. Where do i mistake?