Heya Receptor,
IMHO this site would best fall into hardcore or maybe even groupsex. I don't really see these gals as being 18 or 19, but all 3 galleries have hardcore groupsex action going on.
The only thing that would even appear teen related to me would be the name of the paysite, ukstudenthouse. Look at the site you're promoting and choose the closest niche.
Hope this helps some.