I agree about keeping it one year and fifth year would provide the characters with enoigh experience with magic to be more interesting. It would make it way easier for characters of different houses hang out in clubs and study groups.

[url=http://www.hp-lexicon.org]Harry Potter Lexicon[/url]
[url=http://www.hp-lexicon.org/magic/spells/spells.html]List of Spells[/url]
[url=http://www.hp-lexicon.org/magic/potions-enc.html]List of Potions[/url]
[url=http://www.hp-lexicon.org/bestiary/bestiary.html]List of Creatures[/url]