International student here. I go to a Salesian-run private (as in not government-run) school in Kolkata, India. I’m not Catholic (or even Christian) myself and have never received religious instruction.
What kind of school is this, for Common App purposes?
If the school is not public and has no religious affiliation, it is independent.
But this is a Salesian school, so it has a Catholic affiliation. Therefore, I would call it a religious school.
If the school is a Catholic school is a religious school regardless of your religion.