A person or group cannot be discriminated against because they hold certain beliefs or a religion. My contention is that this was not discrimination. The act of showing an article to a class did not discriminate against any person particularly if the topic of blasphemy covered all religions.
The right not to be offended is different. It is not difficult to offend using satire, Rowan Atkinson, Dave Allen and many more comedians and comics have used satire against religion. Whole books and weekly or monthly magazines exist to satirise all human life. Private Eye and Charlie Hebdo are but two. When has the law been used to act on individuals or groups in this way. Hardly ever, Jerry Springer, Monty Python both unsuccessfully.
Therefore yes religion is protected but not in the way being described by
@Dolph. It would be outrageous to exclude a pupil based on their religion alone. It is not outrageous to teach that pupil using material that may offend some as long as it is done appropriately. Personally I would have chosen differently and shown a clip from Life of Brian to start a discussion on whether it is blasphemous or not. However I can see what the educator was trying to do and that was not to be racist in any way. The cartoons have not been declared illegal or proscribed in any way in this country.