<a href=“http://talk.collegeconfidential.com/community-forum-issues/449521-why-cant-i-delete-my-posts-account-cc.html[/url]”>http://talk.collegeconfidential.com/community-forum-issues/449521-why-cant-i-delete-my-posts-account-cc.html</a>
If you don’t want him to use it anymore (and looking at his posting history as a parent I can understand why - and there are more than 3 posts, some forums are not calculated in the total), just change the password and the email address associated with it.
But there would be nothing to stop him from starting a new account.