If you study curriculum across the world, you will soon realise that we teach more or less the same thing around the globe.
Some curriculums may align the progression of some subjects differently to another curriculum.

To answer the question – No. We do not follow an American curriculum.
Our students are free to choose their own learning paths (and most of them easily surpass any set curriculum).

However, being in Pune, we will try to align to the Maharashtra State as much as possible.

This is so that it is easy for students to move from Flourish and join a traditional school (if they choose to).
However, across the Acton schools, it is quite common for students to jump 2-3 grade levels every year. So at that point, the curriculum does not hold a lot of weight.