Quote Originally Posted by Chuvak
But I imply to say that he has really gone to school with him everyday in his whole school career (except vacations and weekends, indeed).

Really, I wanna clear up whether I can use the Present Perfect Tence with adverbs of indefinite time such as "always" or no (because I was told that this use is impossible anyway, but I've seen in some texts several times that this is not the case)
You can say
"I have always gone to school with him, that's why I know him so well."

This means you went to school with him all your life.
This sounds perfectly natural to me.