For these schools, yes. Top schools generally have either a hard or soft cap on the percentage of internationals will comprise a given class. This is also true for top US universities. For top universities, the admit rate for internationals is roughly half the overall rate. Top boarding school admission percentages is probably similar.
Having said that, you are a US citizen living abroad, so you would not be considered international for admissions, at least for Andover. I’d assume Exeter and Deerfield are similar.