Oh goodness, that's horrible. No wonder you have reservation with group lessons. So would I had I seen something that awful. You are so right in that you have to really be careful when choosing a barn. Thankfully I used to train Saddlebreds and ride in my younger days (hehe) so I knew what to look for. But I have heard stories from friends where one barn the lady was giving her lesson horses ACE to make them calmer for lessons. Scary stuff.
I think most places ask for the minimum of boots and helmets. Helmets are a must for riders under 21.