i want to bring rice to school as lunch but can i still eat it or will it become hard

I have a little lunch crockpot for school. Leave the base at school and only carry the insert home. I have used it for fried rice, soup, and leftover casseroles. If I have something that is fairly dry, I don't plug it in until one hour before lunch.

Yes, you can bring it to school for lunch. Billions of people living in Asia have done so for years.

For example the Japanese have been carrying musubi for centuries before there were microwave ovens.

If you keep it cold with a freezer pack it'll get a little hard, but it'll still be edible. If you keep it at room temperature, it should be fine. If you can microwave it, though, add a little water, cover it, and microwave till it's hot and it'll be almost as good as fresh!