It is never to early for kids to learn

When someone tells you that kids are to young to be taught, I give you permission to laugh in their face. I know from personal experience kids can be taught something when they can communicate with you. The communication does not have to be verbal, but action.
A child can be taught not to litter when they can hold something in their hands. It is a matter of how you communicate this action to a child. I believe the so call grow up just does not want to be bothered. Well it takes more energy to correct a bad habit than to learn a good one from the start.

I know of a 2 year old that is speaking English and Spanish.

It is all in how much effort the parent wants to make in teaching a child.

With the correct positive approach the child will want to learn and learn and learn.
There will be no limit to what a child can accomplish when he or she is older and how they will impact someone's life.