I think Sasha and Spencer did have a good start, but then they started to change all characters to fit the plot point, and all characters became unrecognisable as episodes went by.
As for Matt and Sasha, I like the build up, because Sasha is being written as the character I know, and she is in her "natural habitat", school events. Matt has been written as a multilayered character from the start, and I don't see any plot point whiplash moments, at least not yet.
I have been under the impression that Matt at some point has dropped out of school before, and is supposed to be a few years older than the rest. I could be wrong, but with the way he was with Mrs M in the beginning, these thoughts did pop up to my mind. And his recent situation strengthens this opinion for me.