DS got 4hrs 40 mins per subject in lower 6th, it increased to 5hrs 20 mins per subject in upper 6th. BUT, his school has incredibly long holidays, 2 weeks at Autumn half term, 4 weeks at Christmas, spring half term and then at least 3 weeks off for Easter. And normal lessons stop after summer exams which are the week after summer half term so that they can do time-consuming nonsense AKA enrichment. So if you compare total number of actual lessons over an academic year a solid 4 hours a week is a better deal.
His school also has a head who joked to parents at the leavers dinner about how they had to pay a huge bill for the last term fees despite their DCs not actually being in school for that term. Some parents are struggling to pay fees and are seriously unimpressed.
At my school 5 lessons per week per subject, but lessons are only 50 or55 minutes, so probably on average only 4 h 30 at best. At DCs school 5 x 1 hr lessons per subject. Lots of schools really are struggling to make ends meet though.
My son is at a very large 6th form college doing 3 A levels. He gets 13.5 hours a week plus a tutorial which is 1.5 hours long. This is not due to any cuts - this is how it has always been at this 6th form. So 15 hours sounds fine to me.
My son is taking 3 Advanced Highers (slightly higher standard than A levels) at a state school in Scotland.
They take the course in just one year and he has 5 hours per subject except one subject where he only has 3 hours - there are only three pupils in this class and he'll get a lot more attention so I'm not too worried. This subject is taken from scratch though (it's a social science he's never studied before) so it will be a tall order.
I teach a full time 6th form course (BTEC Extended Diploma) which is equivalent in size to 3 A Levels. The official guided learning hours (published by the exam board) for courses of this size is 1080 hours, which, over two years of school terms works out at 14 per week (that's assuming 2 equal years, which obviously isn't always the case - Year 12 tends to be longer than Year 13) I teach my group for 17 hours per week.