Is it better to have mixed ability classes or to ‘stream’ children for some subjects, whilst ensuring that teachers do still look at the needs of their individual students?

Yes, the research shows a very low effect from ability grouping (d=0.30) – which means it does not matter whether you do or do not group/stream. But the equity issues are damning; and if the grouping is NOT regularly revised then it can set many students into a situation that they cannot get out of even if they wanted. For example, in some subject’s students in retain streams are not exposed to teaching some subjects and this condemns these students to lower streams. This is particularly detrimental for minority students who typically start in lower streams!” (John Hattie, personal communication, December 10, 2016).