TeenTimesTwo I can only speak for DS's school(comp) and although he's in all top sets, the ability range is still very wide and so teaching is pitched to the lower end. I bought DS the CPG revision guides for science and when he compares this to the lesson it has highlighted the material that hasn't been taught or just not taught to the required depth, so if he didn't supplement his learning then no way would he be able to get a 7 let along higher.
Although I have to say the English Dept is fantastic but at the same time it highlights that none of the other departments come even close to what the English Dept are doing.
No doubt in a couple of years when teachers are more familiar with the syllabus and what the examiners are looking for things will improve but that's of little comfort to DC going through it now.