The leader of the Swedish Social Democrats, Stefan Löfven, says that he wants to make it Swedish law that student groups are mixed so that the most ambitious students should be prevalent in all school classes. The reason, he argues, is that it would reduce inequality. It seems as the main issue according to Löfven is performance inequality amongst students – not the fact that many students underperform.
Either way, he ought to read Esther Duflo et al. (2011) ‘Peer Effects, Teacher Incentives, and the Impact of Tracking: Evidence from a Randomized Evaluation in Kenya’, American Economic Review, 101 (5): 1739-1774. This paper demonstrates well through which mechanisms and under what circumstances tracking students may just benefit everybody:
“This paper provides experimental evidence that students at all levels of the initial achievement spectrum benefited from being tracked into classes by initial achievement. /…/ Together, these results suggest that peers affect students both directly and indirectly by influencing teacher behavior, in particular teacher effort and choice of target teaching level.”
It seems logical that the well-being of the students increases if peers are sorted into groups and classes with like-minded people who have similar ambitions and perform at a similar level. It is also likely that students will be more motivated to study if they are not way behind or way ahead the rest of the class in terms of performance. But most importantly, tracking enables teachers to adjust their level according to the needs of the group.
If all students in a school class perform more equally, the teacher will be able to teach at a level and a pace that fits most, if not all, of the students. It is therefore not surprising that Duflo et al. find in their experimental study that tracking benefits students all across the spectrum, both higher- and lower-achieving peers.
A paper by Lars Lefgren ((2004) ‘Educational Peer Effects and the Chicago Public Schools’, Journal of Urban Economics, 56 (2): 161-191) shows that schools using tracking do not have larger differences in performance between higher- and lower-achieving students, which suggests that Löfven’s proposal alone would have little or no effect on the inequality he says that he wants to fight.
There is also another argument to be made for tracking, which has been raised by Thomas Piketty: tracking could result in more resources being devoted to underachieving students, promoting a catch-up. This argument, however, is sometimes rejected by claiming that there is a trade-off. But as Duflo et al. write in another article:
It is often suggested that there is a trade-off between the value of targeting resources to weaker students, and the costs imposed on them by separating them from stronger students. We find no evidence for such a trade-off in this context.