I actually think SSAT has become less useful over time, much like SAT/ACT has, and not using it will enable the schools to take the students they want to have, and who will most benefit from the boarding school education. The fact that many kids now take SSAT three times, with serious tutoring, there are ‘flex’ options where you can take it with your tutor instead of group setting, so many families manage to figure out how to qualify for extra time, it is as much of a function of the resources you have as your academic readiness, if not more.
I don’t think the schools, including the most academic ones, want a class full of academic superstars. They get enough of them regardless, and it benefits everyone to have a bunch of kids who shine in other ways, in terms of their personalities, their extracurriculars, or bring the experience/background the school has been lacking. If the schools are serious about becoming more diverse, there is a great opportunity to make it happen.
And I don’t think the kids who come in less prepared will necessarily struggle, they may get the biggest boost by great teachers and support the boarding school has. They won’t be starting 9th grade in calculus, but that is just fine because all schools have algebra and geometry classes to fill, and are better suited to provide excellent HS math curriculum instruction than teaching college math. Yes our school has a big group of kids chasing curriculum rigor and taking hardest classes possible, but there are plenty of kids who aren’t in honors classes or maybe just one or two and are spending more time taking advantage of the non-academic things BS is offering. And they do very well in college admissions too, because they generally have other things going for them besides academics.
So I definitely see an upside in not requiring the SSAT, and taking chance on kids for other reasons. I think the interview in particular is good enough window to access a student and with all the other pieces of information they can make reasonably well informed decisions.