500
In the fall, your AIMSweb data shows that your class has 20 kids in tier 1, 5 kids in tier 2, and 3 kids in tier 3. In the winter, your AIMSweb data shows that 10 of your tier 1 kids are now in tier 2, all 5 of your tier 2 kids are now in tier 1, and all 3 of your tier 3 kids are now in tier 2. You should probably focus your efforts on improving instruction at which tier?
Tier 1 (Your tier 2 and 3 kids are making improvements and requiring less support, but your tier 1 kids are slipping through the cracks and falling into tier 2)