This is so frustrating while reading, knowing very word but not the meaning. Why double French ? My guess is "they once had French course" based on a fact from the novel. But why double it??? Does it mean "they fail the French test and take the second test?"
here is the sentence :
One of the boys I knew at school had taken a round-the-world trip and come back somehow removed and unknowable, like he wasn’t the same scuffed eleven-year-old who used to blow spit bubbles during double French.
By the way, is it even possible to blow bubbles with spit, as in the sentence "blow spit bubbles"? or does it simply mean the boy likes to spit in a disgusting way ??