Social and emotional skills are crucial for all aspects of our everyday life. However, understanding how digital technology can facilitate the development and learning of such skills is yet an under-researched area in HCI. To start addressing this gap, this paper reports on a series of interviews and design workshops with the leading researchers and developers of 'Social and Emotional Learning' (SEL) curricula. SEL is a subfield of educational psychology with a long history of teaching such skills, and a range of evidence based curricula that are widely deployed in primary and secondary schools. We identify the shared challenges across existing curricula that digital technology might help address: the support for out-of-session learning, scaffolding for parental engagement, and feedback for the curricula developers. We argue how this presents an opportunity for mutually beneficial collaborations, with the potential for significant real-world impact of novel HCI systems, and can inform HCI work on supporting social and emotional skills development in other domains.