After I got your message yesterday, I immediately did google Stephen - it is exciting to find that he was such a powerful figure in the military, but I would think that his involvement with the resolution of the uprising certainly put a different perspective on his service (for some relatives). I found the material you mentioned - the Register, the 1861 census and Charlotte's obit, and several accounts of the court proceedings for the uprising itself.
The school that the girls attended was operated by the Institute of the Blessed Virgin Mary, and is known locally as the Bar Convent because of its location just outside Micklegate Bar (one of the main gates to the city). For much of its existence, few people knew of the convent's existence since it was illegal in the 18th C to be Catholic in England. Louisa and Charlotte arrived at the school in 1833, and Madelena in 1835. I will be able to give you more information on what they studied and how long they were there later this spring/summer when I go back for more research (I didn't include them in my earlier work). It is possible that the other daughters also attended - they may have come ealier or later and were simply overlooked when the original 19th C roster was compiled (one of the projects I am working on is to produce a complete 18-19th c record). I was surprised, however, not to find anything else in the census records for the three girls since they were there in the 1860s.
I would be terrible grateful even for birth and death dates for the girls, and to know if any of them married (the other sisters as well since families often sent the next generation even if the mother hadn't attended, but a realtive had). Is there a chance that you have spouse names for the brothers as well? I'd like to see if the siblings married into the families of classmates, of if their children attended.
Finally, do you know anything about Stephen's family - was he the son of an aristocrat or lesser gentry? Or what Catherine's maiden name was, or anything else about her family? I know its alot to ask, so anything you'd like to pass on would be very appreciated. I'm also curious what other surnames you are researching - perhaps some of them haave ties to the school as well.
I know - I have so many questions!
If you are not familiar with the Bar Convent, you can check out their website - the sisters turned the school over to the York Diocese in 1985, and it continues to operate with several hundred students. The convent itself is now a B&B, and they have a wonderful museum. The school records, however, are not accessible online, nor is there any published material on the students themselves. At this point, the archivist can only provide verification of names and dates from a roster that was compiled in the late 19th century (but which is also missing a fair number of students). But, I will be happy to pass on information on the family as I get it during my own work this year.
Whew! That's a lot to digest, so I should stop and get back to work. Hope your new year is off to a lovely start!