Not to take away from the achievements of the students in those schools, but care needs to be taken to put the statistics with appropriate context (much like the broader school rankings in the media). What these schools have achieved is amazing but it would be misleading to say that Al-Faisal has outperformed James Ruse in maths (by measure of band 6s) when the different levels of the cohort as a whole are not taken into account.
For example, the article notes that the majority of the students in Al-Faisal did Mathematics Standard as a caveat (which James Ruse does not offer) and it is well known (anecdotally at least) that there are practices of forcing perfectly capable students into lower level maths courses. Since the data excludes a significant chunk of their students (it only shows advanced and extension percentages), it would not be correct to extrapolate this to make a general comment about the cohort as a whole.
More context can be provided if you look at where the band 6s are coming from even if you just outright ignore the Mathematics Standard students (which you shouldn't). For Al-Faisal, the proportions of its band 6s in Adv, Ext1 and Ext2 are (66%, 18%, 16%) whereas for James Ruse they are (12%, 52% 37%). This suggests that for Al-Faisal, most of the band 6s are coming from Mathematics Advanced whereas for James Ruse, the majority of its band 6s are coming from Mathematics Extension 1 (noting that about half its students take Ext2).