Visual impairment is common among children in rural China, but fewer than one-third of children with poor vision own and wear eyeglasses. To study the effect of hospital-based vision centers on academic performance, ownership of eyeglasses, and eyeglasses-wearing behavior in rural Chinese children. Cluster randomized, investigator-masked, clinical trial from September 2014 through June 2015. A vision center capable of providing refractive services was established in the Hospital of Yongshou County, a nationally designated poor county in rural Shaanxi Province, western China. All 31 rural primary schools in Yongshou County participated; participants were all children in grades 4 through 6 (aged approximately 10-12 years) with uncorrected visual acuity of Snellen 6/12 or worse in either eye (2613 children). Data analysis was conducted March through May 2016, and data were analyzed by the intention-to-treat principle. After teacher-led vision screening early in the school year (September-October 2014), schools were randomly assigned to either early referral (December 2014-February 2015) to the vision center for refraction and free eyeglasses if needed or late referral (March-June 2015) for the identical intervention. The primary outcome was score on a study-administered mathematics test (June 2015) adjusted for baseline score. Secondary outcomes were self-reported eyeglasses ownership and wear at final examination (June 2015). All 2613 children evaluated were of Han Chinese race/ethnicity, and 1209 (46.3%) were female. Twelve hundred children (45.9%) met the vision criteria. Among these, 543 (45.3%) were randomized to early screening and 657 (54.7%) to late screening; 433 (79.7%) of the early screening group and 516 (78.5%) of the late screening group completed the study. Of eligible children, 120 (27.7%) owned eyeglasses at baseline. The adjusted effect on test scores comparing early and late groups was 0.25 SD (95% CI, 0.01-0.48; 1-sided P = .04), with the point estimate equivalent to half a semester of additional learning. At the end of the study, 347 of the 433 participants in the early group (80%) reported owning eyeglasses and 326 (75%) reported wearing eyeglasses; among the 516 participants in the late group, 371 (61%) reported owning and 286 (55%) reported wearing eyeglasses. In this study, early provision of free eyeglasses was seen to improve children's academic performance and wearing of spectacles. These findings suggest that a county hospital-based vision center may be an effective way to improve children's educational opportunities in rural China. isrctn.org Identifier: ISRCTN03252665.