I can't really comment on the sgian dubh, especially as you were asked to speak, but my youngest daughter had a Thanksgiving day brunch today at her school and we all went to see her and her class perform. I was in a kilt with a sword shaped kilt pin. I never thought twice about it, and nobody else said anything about it, but I did wonder about a sgian dubh when one of the little girls in the class noticed the kilt pin and began playing with it (she was sitting at a child's table and I was standing next to her talking to someone). No real problem, but it made me wonder about carrying a real sgian dubh in the same situation and a child taking it out to see what it was. Now, these are 3-4 year olds, so them taking one out is not impossible and I would not want anyone to get hurt. Older children would PROBABLY know enough to ask what you were wearing and if they could touch/see it, but who knows. Anyway, just something else to think about when visiting aschool.