People can have many different beliefs, this is the entire point of the FSM. That those beliefs should stay in people's homes and churches, and that science should stay in the classrooms, is the secondary point.

While I actually do agree with you that science shouldn't include ID (I can't even see how you could spend more than a day studying ID in science class), I am disturbed by your comment of faith belonging in homes and churches. Can not faith also be expressed in public?

The important bit that the granparent was saying in the quote you selected is that faith should not be in the classroom. Otherwise you end up with even more arguments such as which religion and which branch of a given religion should be taught. There are too many religions and variations on them to try to teach them all and there places better suited for those types of teachings like at churche and at home.