my primary school and 7-10 school were both Dominican (ie catholic schools originally set up and run by the Dominican sisters after St Dominic DeGuzman). all dominican schools have the same motto and similar crests: Veritas or "truth". i got very sick of the whole "it means being true to yourself, working for what you want, and true to everyone else by being a good person" thing.
for religion we had to study the school crest every few years. at my primary it was the DeGuzman family crest overlapped with the Aza family crest (for Dominic's parents Felix and Jane), and the word Veritas was curved above it with a small star in the gap between the word and the crest. Jane supposedly had a dream Dominic would be a guiding star for humanity.
at my 7-10 school the name was written in green in a gold circle. green for australia and gold for our link to the pope. in the middle was a dove representing the holy spirit and it had three gold ribbons from it's beak: for work, rest and prayer. the Aza family crest, the "Lilly" representing change from dark to light, stuck out from underneath it.
i was so glad to escape to a Marist school this year. the motto is Christus Lux Mea (Christ My Light), pretty self explanatory, no lectures. the crest is just a red cross, a boat and a star to represent St Marcellin Champagnat's (sham-pan-ya) (founder of the Marist Brothers) missonary journeys.
our crests are religion lessons in themselves!