I am the principal of an independent school and we administered MAP Growth for the first time this year to 3rd-5th grade. Approximately 20% of each grade (we have around 50 students/grade) dropped 10 RIT points or more from the winter to spring - mostly in Reading and Language Usage, some in Math. It was not necessarily the kids "you'd expect" - many had done quite well in the winter, although not all.
Has anyone else seen a pattern like this? We also started testing much later in the year than I intended for a variety of reasons so there was only two and a half months between the winter and spring administrations; I'm not sure if that makes a difference.