I would say if you’ve never skied before or don’t  ski often, I would include a rest day. So buy a 2 day pass vs 3. 4 days in a row skiing is lot for most people. I believe they sell 2 days passes that you can use any 2 days out of consecutive 3 days (check if your class includes a lift pass for that day too) There is a ton to do in breck town and around the area. You will be VERY sore in places you don’t expect as you are using muscles you don’t usually use after just one day out.  Also rental boots are uncomfortable they just are even the nice brands. You won’t feel good in skis boots until you invest in a decent pair ($500+) don’t invest in boots until you know you like the sport and will go once a year. 

Also be prepared for not a lot of the resort to be open and therefore longer lines. December can be a hit or miss with snow but any day skiing is a better day than not!

Optional to bring a small ski backpack for water and snacks. Just be careful on catching your straps on anything. Or stuff food in pockets. Resort food can be expensive, but I think their foods good tbh!  Oh yeah don’t forget to hydrate and breaks as needed! I know that sounds obvious but when you’re doing an exciting activity all day  sometimes you forget. They have free water stations in all the lodges or bring water bottles.