Whitelists for Overzealous Internet Filters?

Anonymous Coward asks: "We've all seen how plenty of bad examples of Internet filtering in libraries and schools, so I need not list any. After browsing the aforementioned YRO archives &c., I had an interesting proposal. Books that people *want* the public to see are submitted to libraries to be placed on the shelves. So why not come up with a similar solution of the public submitting lists of websites to be *allowed* access from the libraries. Project Gutenberg or The Bible blocked? No problem, just ask a librarian to add the domain to the allow list." Would this be a practical way around overzealous filters?