I work with teens (and elderly) utilising potentially dangerous tools and it’s very straight forward … people using tools must be supervised closely, first aid processes followed (including appropriate medical attention), accidents reported internally/externally, parents informed, first aid training updated regularly. It sounds like this teacher failed to follow procedures. This could be a training issue or an unintentionally neglectful mistake. Either way I hope she has been supported in terms of what action to take when next presented with a burn. We all make mistakes and at least it was a minor injury.