Social sciences librarians have an interest in supporting systematic reviews, but the available guidance is focused on health sciences settings. This study contributes guidance specifically for social sciences librarians using the Campbell Collaboration's standards to evaluate the search methods reported in systematic reviews on K-12 mathematics education. After searching ERIC (EBSCO), Education Source (EBSCO), Academic Search Ultimate (EBSCO), and Compendex (Engineering Village) in April 2018, we included 40 systematic reviews. The reviews were evaluated on the transparency of the reporting and the comprehensiveness of the search as required by the standards. The findings revealed deficiencies in search processes and reporting of search methods. We conclude by discussing the implications of these findings for librarians collaborating with social sciences researchers.