I just found this thread, looking for a pre-K program in French. If you are in the McLean, VA area and know of a program to immerse 4-year olds, please post back.
Our two older kids go the French Saturday School (
myfrenchclasses.org) which is located near the Beltway and easily reachable from VA (we live not far from McLean ... with no traffic on Saturdays, it only takes about 20 minutes to get there).
The great thing about this school is that all classes take place at the same time and that my kids have made friends with whom they also speak French at their playdates. It's very well organized and the teachers are great.
Price-wise, it's the best deal for a real quality program (the classes follow the same books as in France). It's $320 per trimester for three hours a week and siblings get a discount.