Socrates was right.
It should probably be okay to give gifts to the teacher if the teachings worked? Might have to be anonymous. Under no conditions can the teaching be conditional on the gifts, but naturally a genuine instructor can draw high demand, and clearly they're going to prioritize those with bigger gifts.
Perhaps for exactly that reason it doesn't need to be anonymous. Trading little gifts for big gifts is generally okay. It's only bad if someone can't get instruction at all for lack of gifts. However, that just means this teacher is not in demand. They're not teaching because nobody thinks they're worth a gift. Around 99.999% of the time, they're a public school teacher and should not have any authority of any kind.
P.S. Whenever someone 'don't miss' I compare Socrates and laugh.