Does anyone know why Montessori schools cut off usually between Grade 6 and Grade 8? Once you become a teenager does this style of learning not work out? I'd t

Does anyone know why Montessori schools cut off usually between Grade 6 and Grade 8? Once you become a teenager does this style of learning not work out? I'd think if you are in this system by the time you are in Grade 8 and then have to go into a new system it would be more jarring and actually hurt your education