Peer review has been commonly applied to university-level online courses, but less at the high-school level. Little is known about high school students' tendencies when they give reviews to their peers, specifically which posts are more likely to receive reviews. This study adopted social network analysis, regression analysis and content analysis to investigate the structure of students' peer review network and tendency characteristics of peer reviews in a high school SPOC (small private online course). We report four findings: (1) Students' peer review networks appeared to be core-periphery structures; (2) Time is a major factor in that students who posted earlier in writing tasks were more likely to receive reviews from their peers. (3) Interpersonal skills significantly affect the number of peer reviews a student receives. In other words, the more reviews a student gives, the more likely that student is to receive reviews from others. (4) Students with assertive arguments and better interpersonal relationships with peers in offline situations received more reviews from others. These findings might provide insights for course designers and education practitioners to design peer review strategies in high school-level SPOCs.