Hogwarts is a very different place in 1294. These are just some of the differences and similarities between the school that Harry Potter attended and the school that your characters are attending.

Some of the differences are:

• Hogwarts castle is no more. Or rather, it isn't there yet. There is a castle (across the lake), but the school isn't in it. The school's in a large manor (see this thread for floor plans and descriptions of the school), so there isn't a whole lot of extra space. It's a lot more plausible for people to unintentionally bump into each other since there aren't a ton of hallways, and chances are pretty much everyone will know everyone else, at least by face, so there's a ton of thread opportunities.
  
• The school population is tiny - and by tiny I mean that there's ~70 students in the school altogether. This is because of the era - chances are many parents aren't going to send their kids away if they're well off, muggle borns don't always make it very far alive if they start doing magical things at a young age, there aren't really that many witches and wizards to start with, etc. That comes out to between 15 - 20 students per house.
  
• The classes. The school isn't organized like a modern day school is. There aren't many teachers at the school (about eight or so), and even though there are very few students in comparison to how many there are in the books, there's still many more students than teachers. Instead of running classes on a single subject, then, each of the professors is able to teach students about more than one subject, and work with students individually or in small groups instead of lecturing them every couple of days. It's up to the students to go to the professors, study things on their own, and go to the professors for evaluation.
  
• When students graduate, they're pretty much told by their professors that they've learned all they need to and to go off and be grown ups in the real world. Students don't have to wait around to learn "everything" either; they can leave whenever they want to, whenever they need to, or whenever they feel ready. Students may leave (or be 'graduated' from) Hogwarts at any point in the year, not just in June.
  
• Students can start their Hogwarts studies at any time, but most people start between the ages of ten and thirteen, depending on when their parents decide to send them away and when they start showing real magical potential. For more information on this, see the FAQ thread.
  
• Even though there are still Houses at the school, dormitories are not organized by House and year. For starters, we don't have years so it's hard to organize dormitories that way, and since the school's so small placing students by House wouldn't be practical. Instead students sleep according to their age (10-13, 13/14, 14/15/ 16/17+), no matter what their House is. When your character is accepted, they'll be added to the student roster and the dormitory roster, so if you're not sure where they are, check that or ask an administrator.
  
• The school year is year round. There are no holidays except for a week around Christmas and a week around Easter, and unless a student can afford to get home, they generally don't go. Please keep in mind that floo powder is very expensive at this point in history (since it's practically brand new) and therefore most students can't afford to take breaks, and if they do it's generally for a month or more at any given time.
  
• The school's only authority figures are the professors and other members of the school staff. There are no prefects or head students. There aren't exactly many rules that need to be enforced, however, since professors expect students to use common sense. Students are to be in their dormitories by 10:00 each night except Saturday night, when they need to be in their dorms by 11:00. Students are to be inside the school by 9:00 each night. Lights out is at 10:30 (11:30 on Saturdays). Students are not to duel unless there is a professor supervising (such as in dueling club) and dark magic is expressly forbidden.
  
• Classes run every day of the week except Sunday. Since aren't exactly organized classes, though, this means that professors are available every day of the week except Sunday, not that students have to be studying every day except Sunday. Students study at whatever pace they feel like - the longer they want to be at Hogwarts, the less work they do.
  
• Due to the proximity of Hogwarts to Hogsmeade, chances are students and professors spend a lot of time going between the school and the village. Since the school is in such a small building (at least in comparison to a castle), there is no owlery. However, there is a public owlery in the village. Since the school and village are so close, there aren't set weekends for trips. Students can head into the village any time they want, providing it isn't after 9:00 at night.
  
• Students arrive at the school by floo powder, not by train (obviously, since there's no trains at this point in history). The fireplaces are hooked up in the Great Hall. Since students don't all arrive on the same day there generally is not much traffic through the floo network. There are no carriages from Hogsmeade since the students arrive right at the school and the town is within walking distance.
  
• There is no Ministry of Magic. In place of the MOM there is a wizard’s council made up of seven witches and wizards (they are not elected). See this thread for more details about the Council.

Some of the similarities are:

• There are still four Houses! And even better, they're the same ones. Each House does have common room as well, but there aren't really any rules keeping people out of other House's common rooms except common sense and a slight student taboo - it's just something you don't usually do.
  
• The basic subjects that students study are still pretty much the same ones, even if they don't have actual classes.
  
• There's still quidditch because it's awesome. Things are changed up a bit, though, because there's so few students in the school (and the team is made up of 7 players, which is almost half of a House) - see this thread for more information.
  
• Wizarding government might be very different at this point but there are still basic things like aurors and politicians. Check out this thread for some basic information on the laws at this time. Aurors do enforce these laws, as well as local lawmen, and most are punishable by sentences in Azkaban (which does exist, complete with dementors, yes).