Now this is a guess ... Families move / change schools for other reasons, so it's possible (probable) that there will be spots. There just aren't that many children with Montessori experience able to transfer in. So unless the class has room now, your spot will be available based on attrition.

And if parents can plan for a change / move, it would happen at the end of the school year to minimize disruption for their child. So have some faith through spring / into summer. Parents aren't always good at notifying schools of their decision to enroll elsewhere / moves. It may be that the admin won't know for a while.

We enjoyed our experience at RGMS but are one of the families that did make a change during summer. It happens

Our child is waitlisted for an older (elementary) grade. Does anyone know if there's typically a lot of waitlist movement for the K+ ages? Since you need prior Montessori experience I know there are fewer applicants but I suspect that also means that fewer spots open up.