The purpose of this study was to investigate the effects of the expectancy of social support in junior high school students on school stress. 917 boys and girls, from 1st to 3rd grade, completed the Scale of Expectancy for Social Support (SESS), the School Stressor Scale, and the Stress Response Scale. The results indicated that (a) the SESS had a single-factor structure,(b) social support alleviated school stress more effectively in girls than in boys,(c) the alleviation effects of social support were dependent on the differences of stressful events, support resources, or stress responses, and (d) father support, which was less expected than mother support, was the most effective in alleviating stress responses in girls, but not in boys, Finally, the implication of social support for school stress process was discussed.