The value of your site will be not so much based on the name but instead on how you have built up the site and the traffic to the site.
The short answer is what your site earns per year * 3 (maybe at best 5). That is what your site is worth, but knowing the value of something and finding someone to pay this isn't always so easy.
I would consider expanding your site to include lessons for home school kids to maybe expand the potential market for your website. That should help increase the value somewhat.