"Fellépek az iskolában."
Translation:I perform at school.
The other translation given is "I step up in the school". That is the literal translation, yes... that doesn't actually, like mean anything that anyone would understand if you said to them...
(Furthermore, in English we'd say "at the school", unless you specifically want to stress that the performing is taking place within the building, and not, say, outside in front of it)