I was quite the opposite tbh. I really slacked at school and placed more of an emphasis on mucking about with my mates and my GCSEs weren't brilliant despite me being predicted really good grades up until my last year. Once I got to college though I worked my arse off and got some A Levels under my belt.
GCSEs are only mega important when you're trying to get to college or the next step of your education (or if you're going straight into employment), if you do pretty badly then you might have to start on one of the lower level course but once you've got higher level qualifications then the GCSEs pretty much become irrelevant.