Comparing St John's and BIS

I would like to move my kid (15yo) from a Belgian school so he can do the Intl Diploma programme. because of physical location, we would like either one of St John's or Bogaerts Int. School. We could consider ISB if it was MUCH better than these two. Can anyone share their experience, please?

Look into IB results of all the schools.
Surprised you've not mentioned BSB with the best IB results.
However if you are an EU national, you can send to state boarding in the UK where some schools do IB for cheaper than private day schooling in Belgium, in fact for half the price.