It depends upon the child. Each one has their own needs and capabilities.
Children learn meditation very easily, if they are taught properly.
One should be mindful of their age. The sexual mysteries can be explained when they are of appropriate age. Everything else in Gnosis can be studied at any age.
“Nothing is easier than self-deceit. For what each man wishes, that he also believes.” —Demosthenes
"Do not worry; cultivate the habit of being happy." —Samael Aun Weor