Invalid code is irrelevant to crawling, unless there is broken code that affects the links. For instance, I saw a page recently where the comment tag had been opened in the head, but it was never closed, so everything in the page was a comment.

I had a quick look at the site in your signature, and, unless I missed a link somewhere, I'm amazed that Google has indexed more than a dozen or so pages. They probably got most of the 200 from links pointing at them from other sites.

Your problem is that most of the pages aren't crawlable. They are hidden behind forms, and spiders can't fill forms in. You need to make paths for spiders to follow, so they can reach all the pages.

One way of doing it would be to add a directory as an alternative way for people to use the site. E.g. home page -> directory top (lists states) -> state pages (lists cities) -> city pages.

Another way would be to add an alphabar to the homepage, so that people can click a letter to get a list of cities that start with the letter. Clicking on one of those would return the list of schools in the city, and so on.

I may have missed something in the site, but I can't see any way of reaching any state, city, or detail pages without filling in the Search form, and spiders can't do that.

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I've just seen your last 2 posts, and it looks like I've missed something in your site. Or maybe you've changed it to a form-only system since all the pages were crawled.