To be honest, I cannot believe that a young kid needs a $30 per month for two years smartphone data plan. I suppose that it depends on why you want your child to have a phone (and, of course, how young that they are.) To be able to call you when he/she needs a ride? To be able to reach them at any time when they are away from home? There are plenty of feature phones that will allow this very easily for a lot less money.
We bought phones for our kids when they were old enough to be left somewhere - soccer practice; after-school band; going shopping or to the movies with friends; etc. - without our direct supervision or a defined scheduled drop-off and pick-up time. They weren't what I would call young, though. Perhaps I am already too old ...