Montessori school in Springfield/Alexandria

[Anonymous]

We have a 21-month old son and a nanny takes care of him. We currently live in Alexandria and are in the process of looking for a house in the Springfield area.
We want to send our son to a Montessori school next year with a daycare program when he will be about 2.5 or 2.75 years old or so.
So we're not sure if we will still be in Alexandria or Springfield by then.

*Should we be looking at schools now in both the areas for admission by fall next year? When should we start looking? Do we have to pay now to reserve a spot?

*Is it hard to get admission in these schools?

Thanks!