End of last week, my ds aged 3 1/2 came out of nursery school sporting a small gash millimetres from his eye. His teacher brought out the accident book and apologised, saying it was her fault, she thought he wasn't sitting down, pulled the chair away and caught him with it. It hasn't healed yet after a few days, though it's smaller. Is this a little red flag about carelessness or an accident that could happen to anyone in a busy environment?