Teachers not currently registered on a course with the Department of Education, are welcome to apply for a Bodleian readers card. This will allow you to use many of the libraries within Oxford (although not to borrow books) and to access online resources when using a library computer. For Oxford alumni there is some additional access to selected online resources. For alumni of other universities, check what is available to you.
If you are not close to Oxford, your local public library may also provide access to some academic journals online as well as an interlibrary loan scheme.
If your school is part of the Education Deanery, you may be able to apply to be your school's research champion. This allows you enhanced access to the Bodleian Libraries' online resources as well as the above access to the library buildings and reference use of the books.