When do kids go to school in Sweden?

Answer 1

Well, yes and no. Swedes are in second grade when they're eight, however, a sixteen year old would be in the first, or second, grade of what the Swedish, for some unexplainable reason, call Gymnasium.

Answer 2

Primary school, which in Sweden is mandatory, runs for 9 years, from the fall/autumn period a child turns 7.

Beyond this, it is up to the person in question, but secondary education is available, and is free. There are 17 national programs, as well as a number of local and/or individually designed programs, which runs up to three additional years.