We are moving to Seattle from India. Looking for suggestions on middle schools around Bellevue, Redmond that a kid following the ICSE curriculum can transition to smoothly.
There are unfortunately no ICSE schools in Seattle. However, there are still a number of good schools in the city.
You might find the following links useful. They list both private and public schools in the two areas you mentioned.
If you're unsure of what curriculum to choose instead of ICSE, many expat families find that the International Baccalaureate is a good choice as it's offered worldwide. That way if your family has to move again, it will be easier to find a school to transition to. American schools abroad are less common than IB schools but it's still a commonly offered curriculum in most expat destinations so a school offering the national US curriculum in Seattle could also be a good option.
For an overview of the school system have a look at our page on Education and Schools in Seattle.
Hope this helps and good luck with your move.