It was so nice selecting school supplies with my daughter yesterday. It prompted me to look up safer plastics (numbered 1, 2, 4, and 5). Whenever possible, this is what we chose.
And she didn't seem to mind the dialogue that ensued about why we're being mindful of which plastics and other materials we considered. Generally, children embrace the key concerns pretty easily, which revolve around the health of our planet, wildlife and other animals, and human health. My experience is that children are usually happy to make conscious choices.
School materials are often made of plastics, of which there are many kinds. Look for those numbered with 1, 2, 4, or 5. Plastics numbered 4, 6, and 7 are more risky.