That all depends on your school. There is no reason why a student can't go from standard to advanced if they are capable BUT depending on the school's text choices it may be VERY difficult. It is easier if the whole of Year 12 starts with journeys and the same texttype is studied across both courses. The it should cause no problem. When you start with modules you will be a whole 10 weeks behind and will have to do the ctach up at the same time as learning new stuff. This is virtually impossible and no teacher would recommend it and most will not allow it. My advice: Decide once and for all at the end of Year 11 exams.
And DON'T do advanced if you hate reading. The scaling is not worth the grief!