Your children don't need good grades to be successful.
Most of success comes from hard work, persistence, the ability to readjust often, and a lot (like really a lot) of good luck.
Taking pleasure in learning is 10 times much more important than grades.
And the funny part is that if you succeed, you will get good grades.
It is still good to know what's already known. But the teacher isn't the source for that. Google is. And there are skills for getting the most out of Google.
Those skills are teachable, as is the fact that Google isn't reality either.