Belgian student who wants to get into a World Top University

First of all, I would like to introduce myself. I am a 15 years (almost 16) old student who studies Greek/Latin with 5 hours mathematics of the highest level per week; and this at a secondary school in Belgium.
Next year, I have to choose a new direction for another two years. All my teachers do recommend me to follow Greek/Science/Mathematics; with 6 or 8 hours mathematics.
After these two years, I can go to KU Leuven, the top university of my country. But, I have a dream! To study Political Sciences or Economics & Mathematics at a World Top University.
Please be kind enough to let me know if an IB diploma is really a must or not.
Thank you in anticipation.

Welcome to the community! I am so glad you are thinking about the world’s best universities because your ambition for mathematics would be perfect for this kind of environment.

I would highly recommend the IB diplomas as all of the top US and UK universities respect it well. The A Level (CIE) is also a very good option you would be able to take through us.

I would aim to be the Dux (top student of your school) and win the mathematics prize at a minimum.