Most schools (public & private), tend to “overaccept” applicants in the hopes that their yield is fairly close to what they predict year in and year out.  For example, if a school has 300 freshman spots, it may accept 330 students expecting about 10% to turn down an offer.  Schools also may lose students over the summer for various reasons (some kids take their time deciding between public & private or they end up moving, etc) and that estimate is also built in to the initial offers.  Because top SEHS tend to have predictable yield rates, those schools do not go to a second round because the numbers even out by the start of school.  They are some instances, however, whereby schools have had a “larger than anticipated” class size due to fewer than expected declines, so sometimes the following year a school may accept a smaller incoming class, etc.

Principal’s Discretion is a process by which 5% of a SEHS freshman class is accepted via a more “holistic” process of essays, recommendations, evidence of hardship, talent, extenuating circumstances, etc.  That process starts immediately after 1st round acceptances and is built in to the expected freshman class size.  All 11 SEHS have the Principal Discretion process but only a few of the SEHS have second rounds such as South Shore, King, etc.