Collaboration is good. Changing the calendar, however, is not going to be the major contributor to improving test scores. The only way student learning can improve is if districts support meaningful professional development, communities support education (and don't denigrate teachers), and families accept their roles in making education a priority.
I do not feel the change in schedule will have a significant effect on test scores.
I feel strongly that the earlier school year start will have little effect on the standardized testing. I understand that there will be two additional weeks of school to educate the students prior to the tests, for some students this may help but for the most part students that do well will continue to do well on the tests and students that don't do well will continue to struggle.