The third Friday of September is when MMSD schools take an official enrollment count. The links above show these official counts disaggregated by a number of demographic characteristics. Classification of English Language Learners changed in 2013-14, so ELL data from prior years is not comparable to data from 2013-14 forward.
There are many ways to look at student mobility, including examining how students move from school to school during the academic year. The file below shows historical mid-year exit and arrival data for MMSD.