...twenty to go!
We found quite a few articles in the journal: Psychology in the Schools. Here's one from Vol 24, October 1987, pp 346-357: "Effects of Kindergarten Retention at the End of First Grade." It's available at this link for $30.
Here's the end of the abstract:
The two groups, which were equally young and unready at the start of kindergarten, were compared at the end of first grade on seven outcome measures; the retained children were then completing three years of school and the control children two. There were no differences between the retained and control children on teacher ratings of reading achievement, math achievement, social maturity, learner self-concept, or attention. The groups also did not differ in CTBS math scores; the only difference occurred on the CTBS reading test, where the retained group was one month ahead. Based on parent interview data, children who had spent an extra year before first grade were not much different from those deemed at risk but not retained, except that, on average, retained children had slightly more negative attitudes toward school. The study findings are consistent with other available research on transition programs that show no academic benefit for the extra year and, when examined, a negative impact on social-emotional outcomes.
And this is the start of the article:
Educators believe that grade retention is an effective solution for problems of academic failure and social immaturity (Byrnes & Yamamoto, 1984; Niklason, 1984). The latest Gallup poll shows that the public agrees (Gallup, 1986). In striking contrast to the beliefs about the benefits of retention, the research evidence is largely negative, In 1975, Jackson summarized available studies and concluded that, "there is no reliable body of evidence to indicate that grade retention is more beneficial than grade promotion for students with serious academic or adjustment difficulties"
The article goes on to provide the evidence. Here's a summary:
On all but one outcome measure, there were no differences between the retained and the control group. Children who were completing three years of school were the same as their matched controls [those who finish 1st grade after 1 year of K] on CTBS math scores and on teacher ratings of reading, math, social maturity, learner self-concept, and attention. The only difference between groups occurred on the CTBS reading test, where the children with an extra year were ahead of controls by five points. This gain of five points translated into a difference of seven percentile points in relation to national norms, or one month ahead of where they would have been without the two-year program. In parent interviews of retained and nonretained matched samples, there was no benefit for retained children in academic progress or in relationships with peers. Parents of children who repeated kindergarten reported that their children had slightly poorer attitudes toward school than equivalent groups of at-risk children.