There are many pricing options for filtering software depending on the type of filter. Unless you are planning to install a filter on only a handful of computers, you will get the best price by negotiating a group, district, or site license. In negotiating with a filter producer, carefully consider the cost per computer for single, site, or network licenses. The initial cost isn't the only factor to consider. Some Internet filtering packages have additional features that may or may not appeal to librarians.
Several packages track each user's access, maintaining a history of every site the user accesses.
Keep in mind that such records are probably not useful in disciplining students for accessing inappropriate sites unless a pattern can be documented. Particularly when inexperienced students use Internet search engines, some sites that are inappropriate for students may be presented on results lists in a manner that doesn't indicate their contents. Unfortunately, the content of the site may not be apparent from the results list. Ethical considerations for librarians involved in such monitoring will include the requirement confidentiality of library records from the American Library Association. The ethical responsibilities of librarians, as well as statutes in most states and the District of Columbia, protect the privacy of library users.