If you're at an age where you have no idea what racism means then I don't think you were racist. Ignorance is different to racism. Of course they are not mutually exclusive, some people can be ignorant and racist, but in your case, I don't think you were both.When I was in primary school I had very little interaction or experience of indigenous people, I only knew about them through horrible racist jokes. I don't think they made me racist as an adult but I was biased towards a point of view as a child.