With être, rentré gets a letter S in the plural sentence, but not with avoir. Is it a rule?

Question

Accepted Answer

Yes, this is a rule. With être the participle is accorded in gender and number to the subject.

Alex est rentré tard. 
Susanne est rentrée tard. 
Susanne et Marie sont rentrées tard. 
Susanne et Alex sont rentrés tard.

-- Chris (not a native speaker).

Answer

Bonjour Nataly !
To complete Chris's answer, here's a link to our lesson related to the agreement of the past participle (here rentré) with auxiliary être.
https://french.kwiziq.com/revision/grammar/agree-past-participle-with-subjects-gender-and-number-with-etre-verbs-in-le-passe-compose-conversational-past
Note that in some specific cases, you might also agree with the auxiliary avoir, as explained in that more advanced lesson :)
https://french.kwiziq.com/revision/grammar/special-cases-when-the-past-participle-agrees-in-number-and-gender-when-used-with-avoir-in-le-passe-compose-conversational-past
I hope that's helpful!Bonne journée !

Answer

"Vous êtes rentrés" and "Vous avez rentré"