I'm halfway through listening to a 3 hour interview with their head of maths. It's very interesting, tbh, how having a half-full school has really given them something lacking in other schools, namely time to think about what they are doing. Their maths curriculum seems to be designed with lots of thought about what goes where and why, and prescribed methods for teaching each topic. I wish I could say as much thought went into my school's schemes of work, but the truth is we just can't. They've been able to concentrate on KS3 for 3 years while the rest of the country has been getting to grips with the new GCSE which will be more established when they start it. Schools are now getting to grips with A-level with last minute syllabus sign-offs meaning everything's a mad rush. Again Michaela doesn't have to worry for a couple of years.
I teach in a department which is not prescriptive. The SOW basically says 'teach solving equations' and it's entirely up to teachers how and which resources to use. I prefer this, but it is way more time consuming. In Michaela they have a booklet for each topic containing examples, questions and everything needed for that topic for all pupils.
I don't know how their pupils actually get on at maths, but I think it gets more curriculum time than at other schools, and the students also do more practice outside of lessons so I suspect they will do well.