1)Those students were being praised by the teachers (use magister, magistri)
Illi discipuli laudabantur
2) Those soldiers will have to be praised by the leader (use dux, ducis):
Illi milites laudandi erunt
3) The citadel had been destroyed by the enemies (use hostis, hostis):
Arx deleta erat
4) Our actions have to be praised by them (use is, ea, id)
Nostra facta laudanda sunt
5) Those tales are read by you (use vos)
Illae fabulae leguntur