Lawrenceville is home to many Princeton faculty children and not truly a peer of MBS as it is a boarding school that attracts kids from around the world and accepts just 18% vs MBS 59%. This is truly apples and oranges. That said, although MBS may be less academically competitive than some of it’s peers, that doesn’t mean it lacks the rigor required for its best students to gain admission to Ivy schools. Many families will choose a smaller cozier school over an academic powerhouse and end up with equally good college options. Sometimes big fish in a small pond is a good strategy. A top middle schooler can find themselves outranked by even brighter classmates and graduate in the bottom 1/3 at a powerhouse school.
Many top private schools like Andover and Exeter have moved away from AP classes as they don’t want to dilute their classes to teach to the test and colleges are aware of this. Classes are generally discussion based and dynamic as they are at MBS. A lack of APs may just indicate a different approach to learning, not a lack of rigor. MBS is also more inclusive than Pingry etc. in that they (in the past anyway. It’s been a few years since we toured) accept a portion of kids with learning differences which will impact their overall scores. This also creates a richer learning environment according to many experts. Believe it or not, not every student chooses their college based on prestige and you would be foolish to choose a high school based on college aspirations at schools with acceptance rates in the single digits - those schools are crap shoots for every student today.