I very much hope that this story is a hoax, I tried to locate the source on the Internet, but failed.
If it is not a hoax, then it is a huge breach of profession norms- made in a hurry and under stress, but still a breach. One should not put children in the situation of choice almost impossible for them -teachers should remember that. Actually, it is not a good idea to force moral choice on people. In most cases, it is immoral to force moral choice on others.