There is plenty of research that holding kids back isn't actually an effective intervention, for example: http://www.sciencedirect.com/science/article/pii/S0022

There is plenty of research that holding kids back isn't actually an effective intervention, for example: http://www.sciencedirect.com/science/article/pii/S0022440506000550 http://www.sciencedirect.com/science/article/pii/S0022440506... Retained students (the current terminology for "held back") are much more likely to stop attending school early, and on average do not see larger academic gains in their year retained than their equivalent peers who are not retained. The ONLY effective intervention is dramatically increased services for that student, delivered rapidly once the deficiency is detected. Many high performing charter school networks actually use this systematically, but only by overworking their teachers and generally burning them out within 5 years (retention rates at 5 years are frequently <10%, compared to 50% in the broader profession). Most teachers in mainstream district schools are covered by union contracts that limit their required working hours, so for the vast majority of schools even this isn't an option. Actually delivering these services in a sustainable manner is a financial burden American taxpayers appear largely unwilling to shoulder.