You say that they haven't started a new elementary class since the middle- and high-schoolers were that age. Have you talked to the parents of these kids who have been taught at this school for years now? Was the start-up of their elementary class at that time structured similarly and what have they thought about the education?
I agree that a $400 deposit seems reasonable so that they can plan. I do worry, though, that if the class doesn't fly you might have lost the opportunity at the Montessori school for the fall. Would HSing then be an option again? If this other school needs your deposit now, do they have a similar spring deadline for deciding if this new elementary class is a go so that you'd have time to make other plans? On the other hand, since your DS was able to start at the Montessori in January, is it possible that there might, indeed, be a spot for him come fall if necessary, even if you don't give them a deposit this spring?
