Pueros impios pulsare non est bonum responsum . Sed bene docere bonum responsum est. (Is it correct anyways?)
I don't understand why "pueri impii" isn't correct here. Is that not plural? This language needs actual lessons and explanations.
That would be the nominative form. The boys are the object not the subject so you need the accusative case.
"Pueri impii" would be nominative case (the subject of the sentence), but the unditiful boys there are in the accusative case (object of the sentence). However, you could say: Pueri impii magistrum (magister would change too) non docent. :)