You may also want to consider that the first set of scores may have been an underestimate. My ds actually dropped 9 points from spring 09 to fall 09 -- but then gained 19 points from fall 09 to spring 10. I'm guessing he didn't forget info from spring to fall, just had a bad testing day ... Which makes an impressive but not a true 19-point increase over the school year.

Was the last test your first data point?

Mia