The Department of Justice has launched another high-profile probe into Arizona–this time in its public schools. The civil rights question isn’t segregation, per se, but discrimination against teachers whose English doesn’t make the grade.

Arizona schools are becoming ground zero in the state’s anti-immigrant political storm. An untold number of children saw their education jeopardized as SB 1070 terrorized parents and in some cases, forced families to consider leaving the state altogether. Then in August, Latino kids in the remote Ajo Unified School District saw their schoolhouse gate turn into a border checkpoint, as Arizona schools chief Tom Horne tried to thwart unauthorized students who had allegedly crossed over from Mexico.

And now teachers have to look over their shoulders, too. In a supposed quality-control effort for English-language-learner (ELL) programs, the Arizona Republic reports, education authorities are pressuring districts to get rid of teachers deemed not proficient enough in English.

Arizona officials have disputed the Wall Street Journal‘s unflattering coverage of the policy in April, insisting that they’re merely trying to comply with standards under the No Child Left Behind Act.

The Justice Department inquiry focuses on whether Arizona is using "fluent English" as a pretext for discriminating against educators who aren’t native speakers or simply speak with an accent. The probe relates to a wider debate about who gives and receives ELL instruction, and the state’s obligation to educate immigrant children.

In the background is a tense legal battle of Miriam Flores v. State of Arizona, which centers on whether the state’s ELL programs are effective and compliant with students’ civil rights. The controversy escalated in 2000, with a state referendum mandating that schools implement "English-only" instruction rather than bilingual curricula.

As with many aspects of No Child Left Behind, the squishiness of the standard invites political manipulation. The "fluency" question invokes an old debate over the politics of dealing with linguistic diversity in the classroom, whether in the form of slang or an accent.

Horne’s defense of the policy sounds sensible. "This is common sense," he told the Republic. "If you want to teach math, you need to know math. If you want to teach English, you need to be fluent in English."

But just outside that ELL classroom, clouds of anti-immigrant hatred are thickening in the political arena. While police prepare to escalate the crackdown on undocumented immigrants, Gov. Jan Brewer–who appeared rather linguistically challenged herself at a recent televised debate–has enacted a bill to bar schools from teaching ethnic studies, which was widely condemned as a racist attack on progressive education.

In this context, Horne does seem to know his math: each calculated strike against cultural inclusion in public schools adds to Arizona’s expanding right-wing agenda.