The classrooms mentioned include both fluent and limited English speakers. That is not what Prop. 227 calls for. These students' parents could not have chosen the best program for their children because districts have not had time to inform them of their choices. Therefore, many parents are not necessarily aware of their option for bilingual education.
Many parents are in the process of obtaining permanent residency.
Though not illegal, they don't want to ruffle any feathers for fear of jeopardizing the possibility of later becoming American citizens. To them, under 227, asking for bilingual education is like going against the law.