The link is broken on my end for some reason. From what I gather, the site that's up lacks some sort of theme or coherence to give people a reason to join other than because "you hope they will". That will never work. You need a theme. Role playing is too general....what types of role playing? Fantasy? Animals? Movie characters? You'll need to decide if you hope to attract an audience...even school friends.
Even though I've turned the board off, my Redwall site, while it was role play based, actually had a coherent theme to it and some images and stuff so it didn't look so basic. That's what you'll need to do for success.