I think the new BAC is a bit misleading because of the science requirement.
To qualify for it pupils need to have been entered in exams for all three sciences separately and achieved A-C in at least two of them. Because of resourcing constraints, most state comps don't do this - instead their pupils do the science double award where they study all 3 sciences but in lesser depth. This means even their brightest pupils wouldn't count for the BAC.
For example, I wouldn't have achieved it as I did combined science even though I got straight As across the board and went to Oxford (not intended as a boast merely to illustrate).
I wouldn't pay it too much attention - just another government spin on the same results.
Whatever way they dress it up though it still depresses me that any school can be getting less than about 70% A-C grades. GCSEs are easier than falling off a log