Here's a few radical ideas:
1. Have the teachers from across the state meet to create the test(s).
2. Make them subject specific - French, physics, American History, etc.
3. Require teachers to grade the tests and report the results within 48 hours,.
4. Give them some real world consequences.  Fail the test, fail the course.
It's worked in New York with the Regents exams for nearly 150 years.  I have tests in my files dating from the 1870's.