Breakdown of Les filles sont rentrées au vestiaire après que l'arbitre a sifflé.
être
to be
la fille
the girl
avoir
to have
au
to the / at the (masculine singular)
Questions & Answers about Les filles sont rentrées au vestiaire après que l'arbitre a sifflé.
Why is a sifflé in the indicative here? Doesn't après que take the subjunctive just like avant que?
This is exactly what trips up both learners and native French speakers! While avant que requires the subjunctive because the action hasn't happened yet (it's uncertain), après que is followed by the indicative. This is because the action (the referee blowing the whistle) is an established, completed fact. Even though you will often hear native speakers mistakenly use the subjunctive after après que, the strict grammatical rule is to use the indicative, as we do here with a sifflé.
Could we use the plus-que-parfait (had blown) here instead of the passé composé (a sifflé)?
Yes, and it would be very natural! Because the whistle blowing happened before they returned to the locker room, you could absolutely use the plus-que-parfait: après que l'arbitre avait sifflé (after the referee had blown the whistle). However, in everyday spoken French, it's common to just use the passé composé for both verbs when a conjunction like après que already makes the sequence of events completely obvious.
Why is there an -es at the end of rentrées?
This is a quick refresher on past participle agreement. The verb rentrer is a verb of movement that forms its compound tenses with the auxiliary verb être. Whenever a verb uses être in the passé composé, its past participle must agree in gender and number with the subject. Since les filles is feminine plural, we add -es to rentré.