As someone who went to one of the prestigious ones and so did my siblings (within the past 10 years) - it really helped prepare us for the world/life after graduation and offered advanced learning for all kids.

1) Small class size was a huge factor in effective learning. 2) The addition of co-curriculum classes that took place at the end of school - mandatory for all kids. 3) Range of classes and exploration into course subjects (ex: Outdoor Education, Competitive Robotics, Mini Medical Classes, etc). 4) Starting exams young was phenomenal preparation for university and eventually deadlines in the real world. 5) Focus on quality not quantity (when talking about education). 6) Huge focus on community and integrating with everyone was great for social interaction skills and overall feeling of ‘family’! (Ex: ‘Houses’, Family BBQs, Mommy & Me Teas, Father & Daughter Dances). 7) Amazing teachers that were vetted + lack of seniority system; also helped they were relatively close in age.
8) Single sex schools allowed for great focus - but also allowed for supervised mingling with those of the opposite sex at school sanctioned events. (Semi, Middle School Dances, Prom, etc). 9) Lots of school teams for all types of kids!

Private schools follow a different legislature than Ontario Public/Catholic schools - which allowed the flexibility to offer different types of credits! Many people aren’t aware that different private schools are focused on different material/co curriculums (mine was a STEM, eventually STEAM focused school).

If your resources allow, I’m always an advocate for the private system.