During the song 'Only the good die young' Kurt walks past the others to sit on the swivel chair but in the next shot he is nowhere to be seen and then he is suddenly sat on the chair.
Sue's "civics lesson" is jam packed with misinformation about who can do what in the public schools with regards to religion. Staff are very restricted. They can not be seen as promoting or restricting any religious expression. Students, on the other hand, have just as much freedom inschool as outside school to express their religious beliefs. In this episode, the students (as long as they are not coached to do so by Mr. Shue) can sing any religious/spiritual song they wish, even a blatantly religious one, such as a hymn. Sue is the one breaking the law, not Will.