Teens and adults can access practice tests through this program. You can add this free program to your library website.
They are currently running an incentive award program for new library partners: five of them will each receive $500. Have you tried this program? If not, this may be a good time to check them out: http://driving-tests.org/library-award/ (The incentive award program ends 31 August 2017.)
Here is another site to add for your patrons.