I think it's a good idea. Teachers aren't being asked to arbitrate on whether abuse has taken place, merely to take action if they suspect abuse has taken place, by passing information on.
Such practice is not new and corresponds with information sharing processes as outlined in the Children...
It's not a question of knowing that child abuse has taken place. Teachers are trained on possible signs of abuse, and have a responsibility to take action if they suspect that abuse may have taken place.