Request help.. How to ban a class and make it not usable?

Sorry for my bad English..
I played some private servers and they banned a class, Psychic, which is totally freak class when it has a full set of equipment..

Please.. may I ask how to do it? >__<

The process is:
When I choose Psychic to play, the system will pop out a message..
After I click OK, then I will log out automatic..
and then.. the account will get banned..

It's been written here about 32949432859843597390475894395 times, but whatever, for the "special" people who cannot search : ptemplate.conf, allow_login_class_mask. It's a bitmask.

Wew thanks Swwosh91.. I get what you mean! :D