Dear M.(le nom de ton professeur),
I'm very sorry for not coming in English class when you were absent (tu peux rajouter la date de son absence) while the Australian correspondent was present, I know it was disrespectful to her and to you and that's why today I make to you my apologies. I hope you will sincerely accept my apologies.
WIth all my respect, cordially.
N'oublis pas de choisir la meilleure réponse ;)