As I look through one of my WP databases, there’s an ID column, and there’s a GUID column. I’m not sure how your IDs got jumbled up, but WordPress processes page identifiers on the fly.
You will either have to browse through your database with phpMyAdmin, or just go with the Permalinks. Permalinks are much prettier and search engine friendly.
I’m not sure why you’re interested in SEO, since your site has a very specific audience. Just typing in Hill Elementary brings up your site in the #1 slot in Google. Beyond the top 3, the schools are Something Hill Elementary. I don’t think your school will fall far, if at all, without SEO. Here’s a handy guide: