And let's remember reported school SAT scores are not the same.
The public school SAT scores just include the kids that took the SATs. The low performers sat out and didn't drag down the school's scores.
The private schools require ALL of their students to take the SATs.
I am all for private schools but I don't think SAT score is the metric you want to hang your hat on.
You could argue (I'm not) that the difference in SATs comes down to one metric: If you fail a course for the year, you are generally asked to leave the school.
I know that at Loyola, Georgetown and Severn it's rare to find a student with below a 2.7 GPA or so. And there's no coherent argument that any of those are "easier" than public school, so.....it does mean that they either screen out, coach up, or get rid of kids who can't hang academically.