I don't think there are currently any kitesurfing schools based in Lancelin. These guys were there for a while but I think they have gone:
www.facebook.com/pages/category/Sports---Recreation/Makani-Kai-Kiteboarding-147627461948434/I have on rare occasions seen another school give lessons there but I don't know who they were.
Lancelin is a small place. It would be pretty hard for anyone to make a living teaching kitesurfing there. You might have to take lessons in Perth or pay someone from Perth enough to come up to Lancelin. Sorry to have to disappoint you. I hope you find someone.
Or the two of you could try surfing or windsurfing. Werner has scaled back his windsurfing business. He no longer rents gear directly from the beach but from his house. You could ask if he still gives windsurfing lessons.
wernershotspot.blogspot.com