My "oh no" moment

My "Oh no" moment...

My math tests were an amazing success!  Tests on Tuesdays, retests on Thursdays or Fridays.  Things were working, kids were engaged and striving to move up from test to retest, and parents could see and help with exactly what the student was struggling with.  All was going well, until I read to about halfway through Differentiation : Simplified, Realistic, and Effective by Bertie Kingore.  I was convinced of further change in the first few chapters and then started swearing to myself about chapter 5 or so.  What was working so well for tests needed to be done for instruction.  This idea hit like a semi-trailer.  I could see the reasoning.  I had experienced the wonderful results of my initial changes, but this would require an overhaul of how I delivered my lessons.  How could I do for instruction what I had done for assessment?  I started small and I started with math...
Math practice sheets had always been part of my warm-up for each lesson, and I had systems in place for tracking student progress through mad-minute times tables, etc.  I decided the sheets, handed them out each day, collected them, and marked them.  "Challenge by Choice" was one of the catch-phrases in Tiered Teaching, so what if the students just chose their own sheets?  Would this work?  Wouldn't they always just take the easiest sheets?  I decided to try it out.  I set them all up at the back of the class in 6 different bins, and talked with the students at the beginning of class.
"Challenge by choice is like playing basketball.  If as intermediate students you play against kindergarten kids, you get lots of points but you don't improve on your skills.  It doesn't' make you a better player.  On the other hand, if you play against a NBA player, you don't score many points at all (if any) and you also don't really get to improve.  Challenge by choice means finding a sheet at that just-right level so that it drives improvement.  I am not so much interested by points as I am with improvement."
It still took a few weeks or maybe a month before the last of the students were selecting a just-right sheet each day.
Great, this part was working. What's next?