Did Neil lie to Mr Keating in Dead Poets Society?

In the part where Neil breaks the news to Mr Keating (in a classroom) that his father, although reluctant, would let him play in the show, Mr Keating is overjoyed and asks him if he had told his father exactly what he had told him the previous night (the previous night Neil goes to Mr Keating's room and tells him that his father won't let him perform in the play).

Neil stutters through this part (in the classroom) and gives vague answers without much eye-contact. Mr Keating does not look so convinced. Furthermore, his father's extreme anger seeing Neil perform makes me think that Neil had actually never talked to his father about how much he loved acting before he talked to Mr Keating that day. What is the explanation behind this?