One thing in that article that stands out is that the school in question is a Church of England school. That a clearly devout muslim felt comfortable working there, and colud wear her full relgious dress, except where it directly conflicted with her job is a good sign.

But if you're expected to teach English to a group of young children, many of whom have English as a second language and are still learning it, for them to be able to see your lips is very useful.