I am a parent and have been so for years. Harbor is a wonderful nurturing place. The families take nurturing and warmth seriously but dont take themselves too seriosuly. Their is good self-selection here in that parents all have a similar philosophy including not being snooty. They have all the money and power of other families, just dont like to flaunt. The honest assessment is Harbor is a place that is not intense. If you are looking for your child to be a mensa uber learner and leave second grade ready for the Ivy league - Harbor is not the place.
I think Harbor is a nurturing warm environment. The HOS and her lieutenant are lovely warm people. They care and are extremely personable and accessible. Full of shit? No. Salesy - yes. They believe in early childhood education being unique and distinct and either you buy that or you do not.
You will not get prestige of Beauvoir, Sidwell or PDS. But the motivated children and parents have nice acceptances to essentially everywhere they could reasonably desire. Holton, Landon, Norwood and Bullis are the top feeders and I think 100% of the applicants got into at least 1 of these 4. Usually 2 of the 4. I think Sidwell is only by exception (have to have a sibling or hook) and GDS and other top DC privates are rare. But that may be based more on its Potomac/Bethesda location more than anything else. Many others choose public.
There are a range of learners here and I would say that you will be prepared (though not exceptionally well prepared) for third grade academically. The fundamentals are not taught to the top 10% here. In some cases, they need to push more and step up their game. But....
Its 2nd grade and earlier people....so isnt it nice to have a safe warm nuturing private for the tender years? Most children leave understood and fall in love with learning. That is likely more important than anything you could get at this age.... we recommend it and think it is still a hidden gem. Shhhh - dont tell anyone.