(CNN) -- A top U.S. Justice Department official warned Alabama's education department that the state's controversial immigration law has had "lasting" and possibly illegal consequences for Hispanic school children, according to a letter released Thursday.

"(The law has) diminished access to and quality of education for many of Alabama's Hispanic children, resulted in missed school days, chilled or prevented the participation of parents in their children's education, and transformed the climates of some schools into less safe and welcoming spaces for Hispanic children," wrote Assistant Attorney General Thomas Perez, head of the federal department's Civil Rights Division.

The legislation, known as HB 56, has several provisions, including one requiring police who make lawful traffic stops or arrests to try to determine the immigration status of anyone they suspect might be in the country illegally.