https://static1.squarespace.co...97/broomstix_rpg.pdf
You can be any year from 1st to 4th years do a standard 1st year for each year add +1 to any magical skill and +0.5 per year to any skill. Squibs get no magical skills but start with +3 in everyday skills non-magical.
Houses are standard but Squibs are attending placed into House Scalamander with an Owl and colors Red/White they take some classes and attend a Muggle Private School London School of Trades. Hogwarts classes include History of Magic, Care of Magical Creatures, Herbology and one elective from Use of Magical Items, Astronomy or Wizarding Economics. Other classes are off site. Any Wizard or Witch can study for a Muggle Trade or Examinations its treated as Applied Muggle Studies and opens at the 3rd year.
You may run three characters a Student of different years (2) and a faculty member who gets +6 in magical skills and +4 in non-magical skills.