Although the school year here runs from Jan - Dec, the ages/birthdays don't follow this as they do in the UK (Sept - August), they actually go from July - June. Our son had done a term in year 7 in the UK when we moved here in Jan and has a Dec Birthday so we were expecting him to be one of the youngest in Year 7 here, but he's actually in the middle as those in his year have birthdays between Jul 2000 and Jun 2001. Also, the move to senior school depends on whether you are in the state or private system, which really confused me. State primaries run R-7 and 8-12, whereas some private schools move to a 'middle school' in year 6 or 7. Hope this helps!