Grade repetition has been demonstrated to be a poor intervention for academic improvement. Longitudinal studies demonstrate that student grades increase the year following repetition, remain the same when they are promoted to the next grade, and actually decrease drastically thereafter. Students who repeat grades are two to eleven times more likely to drop out. But that is not all there is.
It costs roughly $10,000 on average to educate a public school student each year. Some states and districts spend more, others less. Holding a student back means that another student is added to a school for the retained year and every year thereafter until the child drops out (that is, the added cost is maintained). Some students are held back more than once, adding another year's cost.
So-called social promotion has been demonstrated to be more beneficial to students. They may not be the most contributing members of society, but they tend to stay in school. In fact, across the life span socially promoted students spend an additional year employed.
The government need only implement a real "No Child Left Behind" program and end student grade repetition across the board. That will result in less expense for public education.