I have two children in Montessori and agree wholeheartedly with the above.
I would like to emphasize the check for AMS or AMI. Any school can all themselves a Montessori school, so I'd make sure it's at least certified in one of those two (not familiar with SAIS so cannot comment on that).
JS and C++ are killing it on adoption because they had near monopolies for an extended period of time in their respective areas (browser, native higher level language). They are popular despite their obvious (some in hindsight) shortcomings due to lack of alternatives in the same categories.
Similarly, I’m curious as to what the details of a “slightly less generic” type system entails.