You will find two kinds of admissions in use at American boarding schools: admissions with a fixed deadline and rolling admissions. Let's take a look at rolling admissions and how it compares with admissions with a fixed deadline.
What is rolling admissions?
Rolling admissions refers to a school's practice of accepting applications within an admissions application window and acting on those applications within a couple of weeks or months as opposed to waiting until a fixed deadline to act upon those applications.
How does rolling admissions work?
Let's assume the rolling admissions window opens on September 1. You could submit your completed application on September 2 and expect to have a decision back from the school within a time frame from two weeks to two months. At a school with a fixed deadline for admissions you could submit your application on September 2 but not hear whether your child had been accepted or not until sometime in March, assuming the fairly common January 31 deadline.
Professor Allen Grove explains the various kinds of admissions in great detail. This is a longish but very thorough video which is well worth bookmarking for later viewing.
Many schools with rolling admissions have a priority deadline. You would be wise to submit your application well in advance of that deadline. Once all the places are filled, applications from candidates who would otherwise have been accepted will go on a