The question is too difficult for any student/ any students in the class to answer.
I'd like to know which is acceptable, any student or any students? Thanks a lot.

It's not what would be said.

The/that question is too difficult for any of the students in the class to answer.

The question is too difficult for any student/ any students in the class to answer.

I wouldn't have a problem with: The question is too difficult for any student [in the class] to answer. In US English, anyway.

Misha: "The question is too difficult for any student [in the class] to answer."

"in the class" is NOT optional, since without it, 'any student' could refer to any student in the entire school, or even wider than that!

2. The English version recasts the sentence, but preserves more of the original:

"any student/ any students in the class" :>>> "any of the students in the class"

It appears that my belief, that Americans are apparently happy to play free and easy with the actual MEANING of what passes for communication, holds true.

The crux of the questions revolves not around "in the class," but around "any student/any students." That's why I showed it in brackets. If it makes you feel better, go ahead and include it, but not doing so does not change the thrust of the question one iota. In case you forgot, the United States and Great Britain are two countries separated by a common language. And, yes, you're right, we Americans do tend to separate the wheat from the chaff.

"If it makes you feel better, go ahead and include it,"

THIS HAS NOTHING TO DO WITH MY SENSIBILITIES, and all to do with what you, in a cavalier fashion, term 'chaff': sentence MEANING.

I wrote: " It appears that my belief, that Americans are apparently happy to play free and easy with the actual MEANING of what passes for communication."

QED
I rest my case.

À chacun son goût!