This is about the same as any ski school we've encountered. You show up by 9am and your kids are guaranteed a space in the group lessons. They get out on the snow by 10am.
Register your kids (i.e., do the paperwork) the afternoon before if you want to skip the long line in the morning. There is no morning line for "pre-registered" kids.
Don't buy your kids' lift tickets or rent their equipment prior to enrolling them in the school because these are included in the $100 cost of the school. You pick them up at 2:30pm and get a "report card" describing their progress. If they are going to do the school again the next day, you will keep their rental gear overnight.
Even if they aren't going to do the school the next day, you might want to keep their equipment for night skiing with you. If you return the stuff by 9am the following morning, you aren't charged for an extra rental day.
Don't worry about the kids being hungry, unless they are pretty picky eaters. They are fed snacks, hot chocolate, and a typical kid-food lunch during the day. One of my kids actually complained about all the snack and water breaks.
Each child is placed at his or her appropriate instructional level. Our older son was at the top of the instructional level and there was only one other kid at that level--no matter, he ended up getting a semi-private lesson day for the cost of a group lesson.
Our daughter got tired early and they allowed her to call us on our cell phone so that we could decide whether to come get her or let her hang out in the day-care center with the smaller non-skiing kids.
Your child's experience in any ski school will almost totally depend on how well they like their instructor on that given day.
Personalities really come into play. Our son loved his snowboard teacher so much that we asked if he could be assured of getting him again on day two. There could be no assurance, they said. We asked if he could be hired for a day of private lessons. The school accommodated us and we split the cost of the lesson with the another family whose son wanted to work with this particular teacher.
If your child doesn't like his or her teacher, by all means, ask for a switch. Sometimes the same teacher can be "guaranteed" for subsequent group-lesson days--it just depends on the school's manpower situation and customer demand.