We conduct meta-analysis on a comprehensive set of design-based studies of the impacts of U.S. K-12 public-school spending on student outcomes. On average, a policy increasing spending by $1000 per-pupil for four years improves test scores by 0.0316σ and college-going by 2.8pp. Deconvolution models and formal tests show that the distribution of true effects is approximately normal for both outcomes. Given this, we use estimates of heterogeneity and observable policy differences to produce informative probability distributions of true policy effects. The standard deviation of true heterogeneity (i.e., that not explained by sampling variability) in test score impacts is about two-thirds the size of the mean. Accordingly, testscore effects are almost always positive – ranging between -.004σ and 0.067σ ninety percent of the time. For educational attainment, the standard deviation of heterogeneity is less than half the size of the mean so that effects on college-going are always positive – ranging between 0.5 and 5.1pp ninety percent of the time. Marginal effects of capital spending are similar to non-capital, and effects are similar across baseline spending levels and geography. We do find that marginal effects are larger for less-economically-advantaged populations – particularly on educational attainment. Confounding and publication biases are minimal.