Outfits?

No yellow Ninja Suit.

Fail each class once / fail three classes in a row to get the Dunce hat.

You get a Gold Suit once you purchase all available clothing.

Dude, there's a Clothing shop at New Coventry but mark as Barber Shop because it's also sell hairstyle.
Get your ass over there,buy all the clothing and get your own Gold Suit!

I hope this helping!!

U also have to buy the clothes is the barber shop were the greasers live.

just wanna ask, if I have completed all of the class, is it possible to get the dunce hat if u fail 3 times in a row?(some people didnt notice we can retry the class after graduating)

You apparently don't know anything about bully because there is a clothing shop in all the hair places and no there is no yellow outfit because Ive completely beat it so i think i know

There is no Yellow Ninja Suit. 1000 knockouts get's you the Green Ninja Suit. There is a clothes store in every town except Blue Skies. You need to buy all clothing items at Aquaberry, in Old Bullworth Vale, and the clothes from the Carnival, also in Old Bullworth Vale, also the clothes from the Urban store near thepolice station in Bullworth Town, and all the clothes from The Final Cut, which is also a Barbershop in New Coventry, and lastly you need to buy all the clothes from the School Store. You will then unlock the Gold Lame` Suit (which is actually mostly white) that makes you look like Elvis. There are three ways that you can get the Dunce Cap. Either fail three classes, turn on all the showers, or turn on all the taps.

Hope I Helped

There isn't a yellow ninja suit in the PS2 version, I dont know about the Bully Scholarship Edition I didnt play that one