The double award covers about 2/3rds of each of the three sciences full syllabus (syllabi??!)-
They are taught individually but obvously are likely to be in less depth. My dd is doing all three - though we were originally told there would be an option to do double award, and it seems that increasingly indies certainly are moving away from the double award completely. Fine if you are a scientist, annoying if you are not and you have drop Latin and geography both of which would have been preferable! At NLCS they still do the double award and teach beyond the syllabus - it doesn''t stop them churning out science undergraduates so it is possible. They do so because it narrows the options too much. My dd (year 10) is doing the first modules of all three this summer, the second in spring and the final next summer. Then she'll drop the lot! but I hope will be wiser for it!!