The idea of the experiment arised after I got an advice from our Chief Physicist of Summer School. An advice was to let fast students solve their own list of problems ahead of other children - an obvious advice, but not for me. And then I thought: ok, I need two threads of execution, but why execute them on the same CPU? It's 21st century now, the era of multi-core processors! And here we come to the idea of the experiment: two threads, two teachers!
I asked my good friend Andrei to help me. Andrei is experienced in solving problems from physics olympiads, so he was the best candidate. I handed him a Winter School workbook and asked to choose some 4 or 5 difficult problems (marked with *). He then came to my lesson, sat in the corner and offered anyone who is bored with easy problems to join him. Two of children dared, but one later returned to class.
The experiment succeeded, I suppose. The one who worked with Andrew got very interested and coped with his task. While I conducted my lesson without distraction, which allowed me to achieve almost perfect timing again. Yes, we already know, that this perfect timing was evil, but at that time I didn't know that yet...
We repeated the experiment in the other group later. There also were two children who wanted more, and they both did it well. So we decided not to continue the experiment. Andrei was added to the list of physics teachers so he become able to enter the School without need to be registered each time.
I'm not sure if it's right to separate the class into "sheeps" and "goats" so directly, but seems like children understood it right, so we just "did what we must, because we could" :)
— written on August 21, 2011