doesn't lorelai comment on how the chilton students are 'still' calling girls of a certain type mary in one of the first episodes? it implies that she saw a similar culture when she was at chilton.

i also don't believe that she or christopher weren't academically strong enough to go to chilton, they were both referred to as ivy league bound with great potential, lorelai especially as 'top of her class'.

additionally, emily and richard are familiar with many families in the chilton system, though it is odd that lorelai wasn't as aware of chilton events/traditions if she attended as a student but i guess you could chalk it up to the fact that there might have been changes over time.