1) Boarding school is a unique experience that cannot be replicated by a day school.
2) The "second tier" schools, as you call them, are still excellent. It's not unlike college. The NMHs of the world are akin to Kenyon, Wesleyan etc. Still fantastic places to get a great education.
3) Like colleges, each school has a unique profile and you want to find the school that is the right "fit." Exeter and Andover are huge. Groton is very small. Deerfield is very isolated geographically. Tabor is where you go if you want to sail competitively. Choate's theater program is incredible. etc. Miss Porter's is the most competitive girls' school. You get the drift.

Putting aside the possibility of a better education (although one could probably get similar quality at top local day schools):

1) Kid needs to get out of house from parents (or from divorced/divorcing parents)
2) Parents travel/move elsewhere so less disruption
3) Sports and other extracurricular opportunities
4) Growth opportunity living away from home.

Some people value the boarding experience, period. Where they go is a secondary matter.

Episcopal is filled with local kids that didn't even consider NE boarding schools. Many only apply to local day schools (think Cathedral schools, SSSAS, Potomac, Maret, GP) and Episcopal. There are many compelling reasons to chose a local boarding school. Go tour Episcopal and you will understand why some chose it over other local schools. It is an amazing place! We are lucky to have so many private school choices in our area.

Mercersburg is an amazing place.

Berkshire, Northfield Mount Hermon, Milbrook

I went to a NE boarding school and I loved it. Not sure if it is top-tier or second-tier, it's certainly in the top 30.

Such a beautiful campus, so many great teachers, incredible extracurriculars and school spirit.

Lots of merit-based aid. It is a very diverse school, and unlike some boarding schools, all students had a "work-job" -- not just the FA students.

I can't say enough good things about it.

Alas, OP, I know folks who attended all the schools you listed and guess what - all of them are successful, all are really nice (well, one of the Andover folks is a bit irritating with incessant need to name check his academic credentials). All of them, BTW, attended TT colleges.

Friends are at boarding schools. They live in the Boston area but schools that are a good fit at 45 minutes away so you need a SAH parent to drive / pick up twice a day. After a year of that they gave up and found a boarding school that was a good fit.

Other friends who went - living in a small town with and needed a school that offered more.

Parent got an international work assignment in a part of the world they did not want their children (think Saudi Arabia and a 14 year old girl)

Anonymous wrote:A few locals have small boarding programs (Georgetown Prep, Madeira, Sandy Springs), and doesn't St. Alban's too?

Madeira has a large boarding program - not at all like the other ones. It's a boarding school with day students rather than the other way around.

A few locals have small boarding programs (Georgetown Prep, Madeira, Sandy Springs), and doesn't St. Alban's too?

I went to one years ago. There was a combination of "old boys" whose families have gone there forever, students with parents working abroad or in remote places or places with poor schools, and "speciality" students who were there to do something (usually a sport but sometimes theater, language, etc.) on a higher level than their local schools could accommodate.

None of these situations applies to me now that I have school-age kids, and I also don't have $60k lying around, so we are not considering it at all.

Anonymous wrote:Some kids go because their parents went and had a good experience.

Or parent travel for work and the kids want to go.

This is me but DD did not want to go hence local private (MS) she might still change her mind... DS went (HS) and loved it...

OP here. The replies have been interesting. I hadn't thought about merit aid which it seems some schools that aren't big name like Mercersburg and Episcopal have a lot of.

I guess what surprises me that people who live in areas with really good public schools or private day schools send their kids to these schools. Boarding schools aren't as popular as they seem to be in Westchester, Fairfield County, CT or the Boston area. I wonder if people here have different priorities as private seems to be more of a niche thing here.

Yes, merit based aid is definitely a factor.