At my old school, we had a form of double maths GCSE for the top set. When I was there, we would do both maths and statistics GCSEs.
It was not surprising that it was restricted to the top set, as there was no extra time in the timetable for statistics. So, unlike the more conventional double science course, maths and stats had to share one lesson's slot on the timetable. But there were ways to get around the problems of limited time. With stats already a major part of our (higher paper) maths course there was some overlap, and we were able to produce coursework that was acceptable for both courses.
In theory, one maths lessons a week was exclusively for learning stats. But it was given the graveyard slot of Friday afternoon and would often lose out to more pressing concerns, such as revision.
As our exams approached, this lack of attention did cause a bit of a panic.
Many people took the attitude that they would revise for maths and hope for stats. We were lucky enough to have a fairly consistent teacher through our course. But shortly before the exams we were abandoned and for the last couple of weeks the deputy head (a past maths teacher, I believe) took over.
This led to the slightly farcical position of her asking us what we had already done and receiving a whole class full of blank looks. But, with a couple of weeks "revision" of what we should know for stats, our group did not shame themselves.
Still it would be fair to say that most of us dropped a grade compared to our normal maths score. One thing is certain: if a double maths course is introduced, schools will need to find yet more timetable space.
Richard Reynolds attended a comprehensive in south-east England from 1999-2003