La voix passive with compound tenses vs simple tenses

I am confused. I've been studying la voix passive, however, I encountered something that I do not understand. Please explain. On the lesson for la voix passive with simple tenses, there is a sample: The students were welcomed by the headteacher every year. In French, les étudiants étaient accueillis par le directeur tous les ans. And the quiz I did, there is a sentence: The students were welcomed by the headteacher this morning. Because there was no "étaient", I chose "Les étudiants ont été accueillis par le directeur ce matin. Which is correct? les étudiants étaient accueills OR les étudiants ont été accueillis?? Merci beaucoup. umi

I'll give it a try at explaining it: In the sentence, where the students were welcomed every year, this relates to a repeated action in the past and therefore merits the imparfait tense. Hence, étaient accueillis. In the quiz, where the students were only welcomed once this morning, the use of the perfect tense is indicated since it is only a one-time occurence. Hence, ont été accueillis. -- Chris.

Dear Chris, Thank you very much for your input! Yes, what you wrote makes sense!!!!