Both are correct. Also, I don’t know which was the subject of these quotes, yours is valid so you need to know why.

Will Mr Smith always let you out of class when you are out of class?

If the inversion is used correctly, will is moved to the front of the subject

Mr. Smith Only once in a blue moon, Mr. Smith will let us get out of class early.

Original form of the first sentence!

Please read the following comment on Inversion of auxiliary verbs: https://english.stackexchange.com/. If

I did this: Neither nor inversion (which is helpful

anyway) a: com/questions/469178/english submission-auxiliary-inversion/475907#475907 and this: Not yet neither nor inversion Hope this helps 😉