Read it to me x Read it for me

In this particular context I believe the one with "to" would be the most suitable. When you use "for" in such sentence it would imply that you're reading something for someone, as a favor, not in the way you said which is a favor too in a way, but say you're conducting a seminar in front of the class where your group has to read something, and the person that was supposed to read it has someone else do it instead, that would mean they are reading it FOR them because they can't do it. Whereas with "to" you have the idea that you read something with someone being the target of your reading and to whom it is directed which is what fits the context you described best. However, if you use "for" it wouldn't necessarily be a grammar crime, in fact some people might be more inclined towards using it in that sentence. But if you look at it from a standpoint where you prioritize ideal grammar and which one would be the optimal alternative you'd have to go with "to".