precious, precocious

Precious or precious means of great value, monetary or sentimental--
Gold, silver, and platinum are precious metals.
Pack Grandmother's photographs carefully; they're precious.

Precocious or precocious describes uncommonly early development, most commonly used to refer to the mental development of children--
The child is precocious in speech, but he doesn't get along with the other children.
She is trying to teach toddler to read; she hopes he'll be precocious.

Now that you know that, you can say--
"She encourages the children to be precocious; he thinks it's a waste of their precious early years."