If you really want to go there, "you and I" is never correct by the rules of English grammar. It's only when we apply the foreign rules of Latin grammar to Engl

If you really want to go there, "you and I" is never correct by the rules of English grammar. It's only when we apply the foreign rules of Latin grammar to English that we wind up with things like "you and I", which needs to be taught. It has, however, become a marker of education and good manners, so even though it is manifestly incorrect, it is often a better choice to use it in subject position in formal circumstances. Expectations outweigh correctness in this case.