I don't think it's offered here, but in my country and probably other western countries NETs originate from, there are teaching degrees where you specialise in both primary and secondary, or middle years. Come to think of it, I know of some local teachers who have switched between primary and secondary here too, so maybe there is also such a qualification.
And about the pay - you don't become a teacher for the money. You won't last long if that's your priority.