“What pain relief can a 12 year old have?”

It depends on the severity and cause of the headache. Tylenol (Acetaminophen), Ibuprofen or Naprosyn (Aleve) in appropriate doses are usually acceptable initial first steps for mild to moderate headache.
Physician should be cosulted if headache is very severe at onset, associated with other symptoms, does not respond or responds on;y temporarily to one of the medications stated above.