Alex Rider: Wit and Weapons

An F?

Continuation from an offhand comment made in 'Sneaking Out'
It was very rare that the friends and family of Alex Rider would ever meet. This is, of course, due to the indisputable fact that they are collectively dead; courting death by way of work or play; and/or on a different continent. When they do meet it means a humiliating day for Alex.
"I swear he's getting lazy!"
"I am not!"
"Oh he sure is! Did you hear about his F?"
"Guys! Come on! It's normal!"
"Yeah, it was in French wasn't it?"
"No way! He's fluent, remember?"
"Apparently, 'he was tired'. I mean, seriously!"
"I really was!"
"Cub, the last time I tried to wake you, you cussed me out fluently in at least three different languages before you even opened your eyes. French was one of them. 'Tired' is not an excuse."
"... Well! I'm going to go shoot things. And you losers can stay here gossiping for all I care!"