one of the documented procedures in this installation of the ACS
edu_get_user_role   db   user_id   group_id
What it does:
This returns the role the user has within the group
Defined in: /web/philip/tcl/education.tcl

Source code:

    set role [database_to_tcl_string_or_null $db "select pretty_role 
           from user_group_map ugmap,
                edu_role_pretty_role_map role_map
          where user_id = $user_id 
            and group_id = $group_id
            and ugmap.role = role_map.role"]

    if {[empty_string_p $role]} {
	return "None"
    } else {
	return $pretty_role