Two Rivers had one of the highest re-enrollment rates last year, per the PCSB. Certainly no school is a match for everyone who enrolls, but it's just not true that classes change completely, or anywhere close to that.
88.9% re-enrollment, and that's encompassing middle school, where as PPs have mentioned, more attrition does happen than at elementary, for a variety of reasons - including those who are happy at TR but want a secure/different path through high school. It's a high number even compared to strong charters that are elementary only.
Pulled it up here:
http://dashboard.dcpcsb.org/comparison. Expand the last +, leading indicators, for re-enrollement numbers.