15 years in a 6th Form College in UK was my background, teaching a specialised subject (Accounting). I knew when we moved I wouldn't be working in the same environment. I have only worked in the private (Catholic) sector in Qld, and after 5 years I have carved a new path in terms of General Maths (Maths A) and junior maths. In a 5-12 school I have had supervisions well out of my comfort zone, from Y5 French to Y12 Drama. Plus, you might also get some RE to fill up a timetable initially. Probably wouldn't get Y12 classes in your first year, need to prove yourself. Also, don't underestimate the difference in assessment compared to A level.