From my experience, science A levels (I take bio and chem) are far more detailed. The material can be complicated but not mind boggling. It just takes work. They occupy a lot of time and you must be committed to always completing work outside of lessons; generally an hour for every hour at school is recommended but realistically it's about a one hour at home for every two in lesson ratio. Maths is difficult but, as with all A levels, the jump is doable. I got an A* at GCSE and have achieved As in tests, but at the same time, I've also only got a C on several occasions. I'd say if you get an A at GCSE, you would be expected to get a B or a C at A level but this is all dependent on your level of work. If I did no work outside of lessons, I would probably got a C despite my A* at GCSE, whereas someone with a B at GCSE might put in lots of work and come out with an A. At A level it is far easier to fail though. At GCSE, the A* mark for many papers in science can be about 60%, whereas in A level this would be a C or a D (Also take into account the material is much harder). Overall though, I think the jump is over hyped. The work is definitely far far far far harder, but it is not impossible as it is made out to be. It's all about your commitment. Those who work achieve and those who do not, fail. Getting straight A*s at A level would be a major achievement. I'm not sure exactly how it works, but you have to get 90% in a lot of modules which is incredibly difficult. Whereas at GCSE, at least a few people in every year get majority A*s. No not taking triple science wont hold you back as the material is totally new