Have not used either system, but I do know someone who runs a more-or-less RSM. Obviously, implementation will differ from place to place. The center I know about is run by a trainer of math teachers, who is actually very nice (almost to a fault), and places students by assessed instructional level, not age/grade. We haven't used their services, as we feel comfortable teaching our kids ourselves, but know many people in our larger community who do. Mostly high average to MG kids, admittedly.

...pronounced like the long vowel and first letter of the alphabet...