Search the Internet for O level papers from 25 years ago. You'll find in the same subjects that most of what was taught to 14 - 16 year olds then is now in today's 16/17 year old AS level syllabuses, with bits appearing even in the A2 Level.
What has changed is the volume of pointless sh*te that 16-18 year olds are expected to do - "pump up the volume". Poor pre-university kids have to waste hundreds of hours on waffle: Citizenshit, General Studies, Team Building, Numeracy etc. Back in the days when qualifications meant something, these kinds of skills were developed through voluntary work, activity weekends, sport etc, with no exams unless you wanted to get certificated.
Nowadays, you have every skiving moron under the sun getting Es and Ds without lifting a finger. You have students doing A Levels who can't work out a basic percentage in their head, add two numbers together without a calculator and don't have the ability to string a sentence together that makes sense to at least 50% of the Engliush-speaking world. Unluckily as well, there are now so many joke A Levels around that the whole system has been undermined. Still, students who finish Uni with a Media Studies degree (third class), a £20,000 debt with no job can feel very proud.