Update: Thanks to David for confirming that a child language pack such as en_us can be set as a parent of another language pack. Thus, the en_us_k12 language pack now has en_us as parent.
Update: Thanks to David for confirming that a child language pack such as en_us can be set as a parent of another language pack. Thus, the en_us_k12 language pack now has en_us as parent.