Sometimes it is helpful to simplify a complex sentence to find the answer. In this case, we start by observing that English has a
Subject (S) Verb (V) Object (O) sentence order.
Looked at this way, your sentence can be simplified to:
Parents (S) teach (V) children (Indirect Object) something (Direct Object)
Your real question concerns the Direct Object which is itself a sentence. So you are asking which sentence is correct:
a) What (S) important (Adj: adjective) is (V)?
or
b) What (S) is (V) important (Adj)?
In the above sentence, “is” is a linking verb and is followed by a predicate adjective that describes the subject.
So the answer above is b) “What is important”.
If you want to learn more about predicate adjectives, take a look at:
Hope this helped!