Today is the "Père Cent" (Father Hundred) - one hundred days before the Bac exams start - and it signals high jinks outside the lycées of France as the pupils in terminale throw food at those in the years below them.
This year the proviseur has sternly told pupils that the Père Cent will not be tolerated. Also Catrin's school day doesn't start till 10am. Also she's in Terminale, so she should be the sniper, not the target. Also she's promised her friend, Paloma, that she'll be at school because most of her friends are just taking a day off.
But because it's not just her school that's involved in Père Cent she's decided that if she gets to the bus stop and sees a flour and ketchup fight going on she'll just stay on the bus, go round the circuit and come home.
Late News Update : Catrin got safely and cleanly to school. There were a few flour-warriors, but she walked right through them.