So learner drivers or teachers don’t bother learning basic hand signals anymore?

I had my hand up to signal “stop” to a learner who was trying to turn into a side street from the other direction, across a clear way with 2 lanes of traffic. I was in the right lane and could see a car flying up the left hand lane in my side mirror. The learner waved at me, and made the turn without any attempt to see if both lanes were clear. I got on the horn and the car in the left lane screeched to a holt, only just missing the oblivious learner and teacher.