Bobbo:
That site is big, lots of content on the first page, pay close attention to the size of the pictures, the aerial pic of the new academy is about 95K by itself.
Also, check this report, http://whois.domaintools.com/schooldesk.net, it says that your site is hosted on a server with 27 other sites. Are those sites also yours or do they belong to other people? Unless you know about the utilization, traffic, and maybe deficiencies of those sites the optimization of your site will not be easy to do, you will get inconsistent results.
Another analysis to look at is here: http://www.port80software.com/. Go to the green square that reads "Test your site's performance", enter your URL, and click Check. You will see that with compression you can reduce the size of the downloadable content by about 80% since your site has a lot of text!!! If you can, setup compression with IIS, if you cannot do that, explore the use of the DNN compression feature.
I also tell users to check their connection speed with the test on http://www.speakeasy.net/ going to their nearest city (although a test to the furthest city is also interesting), and tell them to keep the address handy so that they can run it at different times of the day. Remember that the speed for most DSL and Cable Modem connections is not guaranteed and varies with the bandwidth utilization of the whole neighborhood.
One more thing, do you have a "Keep alive" solution? If you don't, the first person to hit the site after a period of inactivity will get an unusually long delay.
Anyway, I would start with tweaking the resolution of the pictures and then play with compression.
Hope this helps.
Carlos