It happened to me too just the other way round because I joined the extra classes and the teacher gave us questions but didn't tell us that was what was coming for exams. But looking back I see the unfairness in what he did.
Because then again if I have no money to join the questions would have eluded me or if I was that good then again, the questions would have eluded me. But sadly, that is how the world is.
Honestly, we start learning how to be corrupt right from the basics. It’s really sad seeing these things happen to us as kids.
But such is life.