How was James Head Boy without being a Prefect?

[spi00000000]

No: HPFGUIDX 76864

Newbie response-----

I have a theory. When Lupin or Sirious(can't remember who said it) 
Said that Remus was the prefect and none of the rest of the friends-- 
maybe he was just refering to FIFTH YEAR. Remus was a fifth year 
Gryfindor prefect, But what if JAmes was made a prefect in sixth year?

Spi-- going back to lurking.