Have a read of this discussion about the pros and cons of the IB program. It may give you a better idea if it is something that you would like to try.
The O-Level (Ordinary Level) is a subject-based qualification conferred as part of the General Certificate of Education (GCE). It was introduced as part of British educational reform in the 1950s alongside the more in-depth and academically rigorous A-Level (Advanced Level).
The Advanced Level General Certificate of Education, commonly referred to as an A-level, is a qualification offered by education institutions in England, Northern Ireland and Wales. It is also offered by a small minority of institutions, typically private, in Scotland, where students usually take Highers and Advanced Highers of the Scottish Qualifications Certificate instead. A levels are usually studied over a two year period and are widely recognised around the world, as well as being the standard entry qualification for assessing the suitability of applicants for academic courses in UK universities.