The International Baccalaureate (IB) Diploma Programme, often colloquially referred to simply as "IB", is a prestigious and rigorous educational programme taught in one of three languages (English, French or Spanish) and is intended for students in their final two years of secondary school, often before entering university. It is taught in 1,921 schools, to a great extent in international schools, in 124 countries (as of 2007). The programme, administered by the International Baccalaureate Organization, is the only widely recognized pre-university educational programmes available the world over. However, it remains less popular than nationally affiliated preparatory programs in most countries, such as that of the Advanced Placement examination system in the United States and the A Level or Advanced Highers system in the United Kingdom.
You be better off studying As levels got get into Oxford University. To gain entry you must have at least three As Levels to get in plus sit an exam if English is not your first language.