If it fits your lifestyle, you may want to see if there’s a dcpr co-op near you. It’s half day and fairly flexible about attendance.

Crestview Montessori is on the DC/Maryland line and has a morning program from 8:45am-12pm. Close to Friendship Heights metro.

If you are serious about applying to private preschools for this fall, you had better jump on it as deadlines are usually in February, and admissions decisions announced in March.
You should also play the DC school lottery and see what you get - maybe you can ask the school if they’ll let you do half days for the first month, or maybe your child will be ready for a full day of school come fall after all.