Although the field of Physics Education Research (PER) has some overlap with Education, Cognitive Science, Psychology, Computer Science, and other disciplines, it has its own distinct identity, concerns, perspectives, and approaches.
SRRI's Physics Education Research Group (PERG) does PER.
Wikipedia has an entry on Physics Education Research.
We no longer keep a list of links to PER groups, since our list invariably becomes obsolete and inaccurate. Instead, we refer you hopefully-authoritative link lists maintaned elsewhere: