Why, in these sentences, is the verb placed at the end of the noun clause -
I wonder if he's coming.
I don't know where he is.
Do you know what time the concert starts?
But in these sentences, verb position is different -
I wonder why she called me.
I want to know why they left early.
I've never taught noun clauses before, and the class I'm working with is what I consider low intermediate. It's going to be difficult for me to explain this anyway at their level of understanding - for example, what was taught prior to this was the difference between past simple and past continuous.
But the book we're using insists on the students learning noun clauses at this point.