With the growing emphasis on developing 21st century skills among today's youth, there is continued optimism about the possibilities granted by increasing access to networked technologies, particularly for encouraging youth to pursue their interests and take ownership of their learning. Yet, research demonstrates the importance of adult support in realizing the promise of achieving these outcomes. Designers of such systems are thus faced with the need to create youth-centered spaces that also provide adult facilitation of learning. This paper presents an adaptation of the traditional heuristic evaluation method which provides designers of online learning systems with a holistic view of how adult learning support is enabled across the system. We describe how the heuristic evaluation method was adapted, and through a case example analyzing one online social learning system used in a middle school context, we demonstrate how it can be used to help identify areas for improvement and promising areas for further research. We also present a framework of heuristics which reflect specific educator learning support roles that have been found to be important for youth learning, particularly for supporting 21st century skills. This work contributes a novel heuristic evaluation method that can help designers of online learning platforms attend not only the experiences of learners, but also to how educators are enabled to support their learning.