Fifty years ago, schools used to be single sex.
These past tenses are used to express:
-A finished action or state that happened at a definite time in the past (Past simple)
I saw an interesting film last night.
-An action in progress happening at a specific time in the past (Past continuous)
We were having dinner when someone knocked on the door
-An action or state that happened before a past action or state (Past perfect simple)
When we arrived at the theatre, the play had already started
-An action in progress that was happening before another past action (past perfect continuous)
When she arrived he had been waiting for over an hour!
-Things we did in the past but do not do any more ("used to"+infinitive-for actions and states- and "would"+infinitive-only for actions)
My father used to smoke a lot, but he gave up some years ago.
When I was a child, we used to live in the countryside and we would walk to school every day.
If you are interested in looking into Narrative Tenses more closely, you can check out the following PowerPoint presentation:
Narrative tenses new english file advanced, Past simple, Past Continuos, Past Perfect Simple, Past Perfect Continuous, Action/ State verbs, Used to / Would, from Lola Domínguez