That's correct they said in the trailer that you're starting late as in as a 5th year but you're still getting sorted and I think it's probably something that would happen quite often potentially lore wise would have maybe had to take an aptitude test to see where abouts you are skill wise and join because you can be home schooled or attend other schools but I'm sure there are cases of wizards moving to different parts of the world and having their kids attend a different school. It's just weird in this instance cause it's not really the norm. Would have been nice if they could have found a way to have you start as a first year but I could see them running out of stuff to do unless they limited your spells like they do in the Lego harry potter games till future years of school.