Let me be clear on this point, I am just as opposed to social promotion as I am to retention. Why? Both are products of the assumption that time is constant and that the best way to organize and educate is by batching same-age children together, taking them through a series of disconnected and prescribed content-based coursework, evaluating them via grades and age/time based tests and then either sending them back for re-work or moving them down the assembly line incomplete because it is "time" for them to move to the next set of curriculum.