My husband moved in the 70’s from Connecticut to Minnesota and dealt with this same issue- New Math in one school, then not in the other. He is very bright, but ended up behind in math, confused and frustrated and hates math to this day. He has argued with me about how stupid it is to have imaginary numbers and other aspects of math that went on to impact him in chemistry and physics as well. I believe that if he did not go through this confusing period, he would have likely excelled in these areas.
Now I fear what the impact will be for our students that were thrown into the New York version of Common Core mathematics. Suddenly 5th graders were expected to masted math topics that had previously been part of the the 9th grade Algebra I curriculum, with no process developed to build up this expectation over time. We are left again with a mass of children that were caught up in the confusion of change- left to feel like mathematical failures. It will be a significant challenge to change the mindsets of both our students and teachers to promote positive attitudes and higher levels of success in mathematics.