Question

The principal impressed__us the need for maintaining discipline

Answer 1

heya
I think it will be on

Answer 2

Cambridge English Dictionary defines "preposition" as " in grammar, a word that is used before a noun, a noun phrase, or a pronoun, connecting it to another word."

"On" is a preposition, which according to the Cambridge English Dictionary, means "used to show that a condition or process is being experienced." This meaning is according to the context of the sentence.

So, the correct sentence is :

The principal impressed on us the need for maintaining discipline