When I was placing my Hogwarts cars on the layout for the first time, I made the mistake of just putting the coaches on the consist in the order that I took them out of their boxes. Apparently how I placed them was a major breach of social etiquette, which my daughter was quick to point out..... somehow the numbering on the coaches reflects the seniority of the students who should be in that particular car. In my ignorance, I had (shudder!) somehow put the Freshmen (or whatever the English term is for freshmen) where the Seniors should have been! I don't recall exact details now, and the Consist Seniority Awareness Coordinator is still in bed so I have no way of getting the info. Just be aware that if you have a big time Harry Potter fan in your house, they will know if the order is wrong!
Have a great Sunday
Tim