It can be either what you'd dreamt of, or what your DC would love.
I was always desperate to board somewhere on the coast or on a little Scottish island. Somewhere dreamy with lots of swimming, playing outside, a tiny village shop to visit.... in school you only learn History, Textiles and English :)
Oh! And also Ballet and Music lessons, plus a big school musical once a year (I played Tallulah in Bugsy Malone when I was in year 5 and had decided I would be a famous actor on the West End).
Ah I wish someone would open some tiny dreamy schools.