Preventing page title from showing on single post pages

Atahualpa is a great theme.

It would be great to know how to prevent page titles from showing on single post pages while showing on all other pages (except the homepage).

Here's an example of the problem: http://makingmindsmatter.com/2009/10/30/cheap-schools/

On this page (and all other single post pages) my post title appears twice. I would like to get rid of the top one.

I added this code to create page titles:

<h2><?php wp_title(); ?></h2>

What I don't know is how to write code to prevent the page title from showing on single post pages.