Despite the appeal of promoting and forming collaborative relationships between schools, empirical evidence for an association between school-to-school collaboration and school outcomes is still somewhat lacking. This study utilized data from 76 schools nested within 56 districts in the United States to examine the association between a school's reciprocal relationships and school outcomes by employing social network analysis and hierarchical linear modeling (HLM). After controlling for school and district demographic characteristics, we found the indices of reciprocal collaboration are associated with the school's 2018 student proficiency level in both math and reading and the growth in proficiency level between 2017 and 2018. The implications and limitations were discussed.