Online mentoring provides an effective means of extracurricular gifted education for talented girls in science, technology, engineering, and mathematics (STEM). Comparative studies on the effectiveness of one-on-one versus group mentoring are lacking, however. The authors investigated this question in the context of a Germany-wide online mentoring program that employed both approaches. Study participants were girls enrolled in high-achiever-track secondary education in Germany (N = 347) who were mentored online by female academics in STEM for 6 months, in either one-on-one (N = 156) or group mentoring (N = 191). It was assumed that the specific many-to-many group-mentoring condition examined in our study would be more effective than the one-on-one mentoring condition with respect to (a) the proportion of STEM communication and (b) the extent of STEM-related networking, both of which are important predictors of successful mentoring. Furthermore, the authors (c) expected more growth in elective intentions for the group-mentoring participants and (d) assumed that participants’ centrality in their respective STEM networks would predict this increase. The study presents empirical support for all four assumptions and thus suggests that the special form of group mentoring examined here may be a more successful measure of extracurricular gifted education for girls in STEM than one-on-one mentoring.

Mentoring has experienced a tremendous upswing over the past decades, which has only recently slowed down somewhat. One possible factor explaining mentoring's popularity are numerous case studies suggesting that it is one of the most effective ways of helping individuals to develop. Meta‐analyses indicating effect sizes for mentoring that are below what would theoretically be possible appear to contradict the success stories, however. This circumstance raises questions about the professionalization of mentoring practices. We focus on seven key issues for future efforts at professionalizing mentoring. Key issues 1 and 2 address observation of the state of the art within formal mentoring when programs are planned and implemented: the consideration of recent research and of best practices. While both areas can overlap, they provide complementary sources of pertinent information for the professionalization of mentoring. Key issues 3–6 address the need to align mentoring activities to the specific context and goals of individual mentoring programs by observing idiographic program characteristics, mentoring dynamics, the orchestration of mentoring goals, and the provision of mentoring resources. Finally, key issue 7 highlights ongoing evaluation as the basis of the effective, continuous improvement of mentoring programs.

Although participation rates of women in science, technology, engineering, and mathematics (STEM) are continually improving, low rates are still an issue in many countries. While previous studies found positive effects of online mentoring for increasing girls’ interests in STEM, research concerning explanatory mechanisms is lacking. We found evidence that in a 1‐year online mentoring program for girls (age: M = 13.82 years, N = 998) in STEM, suitably implemented mentoring (operationalized via relationship quality in a program that systematically incorporates structural and organizational aspects of successful mentoring) was associated with positive changes in the learning environments of the mentees (as indicated by their increasing educational capital). These positive changes were associated with increases in the program‐related mentoring outcomes STEM activities and elective intentions in STEM. Finally, we found that suitably implemented online mentoring was indirectly related to an increase in these two mentoring outcomes via an increase in educational capital. These results indicate the importance of paying close attention to learning environments when planning interventions.