PM I am not sure what you mean by small schools. Do you mean new scools with few grades or do you mean schools with all grades but few students.
Regardless you did not respond to any of my issues. If your theories are correct (ie centrist conversion and new school discovery) than we would see those numbers reflected in the grade by grade breakdown. In addition you did not explain why you consider the sudy to study growth more credible than year to year especially when there seem to have been at least some scool reclassification.
Re the blip averages taken over 17 years are not a blip. Yes in some years the growth rate is lower and in some it is higher. The average and therefore the expected value over time is about 3.5% (or 3.2).