But now the mug war is spreading. Not long ago, the Diary reported on a range of mugs from the National Secular Society bearing slogans like, "Schools are for teaching, not preaching" and "Faith is believing what you know ain't so" being sent into staffrooms.
Now the beleaguered Christians have had enough. The Association of Christian Teachers has announced a competition to find slogans for its own mugs and promises to have its Christian cups in the hands of sympathetic teachers by the end of the summer term.
Chief executive Rupert Kaye said ideas for the slogans so far include "I'm a Christian I not a mug" and "Called by GodI but shouted at by parents".
Plenty of room for new ideas then.
Email your suggestions to firstname.lastname@example.org by June 4 and you could win a set of six born-again beakers.
For the rest of us, Mr Kaye's offerings will cost pound;5 compared to the National Secular Society's pound;4.99.
"For the extra penny, you get God. That's not bad value if you ask me," he says.