How do you define graduation

Eric's working on a story for the paper that's quite interesting on both sides.
According to Texas law, students must pass the TAKS test before they can graduate/get a diploma from high school.
Twenty-one students in Waxahachie did not pass the TAKS test. They met all the other requirements for graduation, grades, attendance and so forth, but they didn't pass the test.
From my understanding, the school principal is not allowing students who failed the TAKS test to walk at graduation.
Parents of course are upset and are saying their kids have met all the other requirements and should be allowed to walk.
Some are claiming it's a racial issue (which simply turns me off).
The school says the students were told at the beginning of the year that passing the test would be a requirement for graduation.
Last year students were allowed to walk and simply given a certificate of completion. Another test was given during the summer to allow them to get their diploma but only a very small number came back to take the test.
Should students be allowed to walk simply because they met three of the four requirements for graduation?