CHAMPAIGN, Ill. (AP) – Researchers say an Illinois law that locks in tuition rates for in-state students appears to have the unintended effect of driving up tuition for out-of-state students and fees for all.

The law, which took effect in 2004, guarantees that a student starting as a freshman at a state university will pay the same tuition rate for four years. Only three other states have similar laws, Oklahoma, Texas and North Carolina. A recent study and another published last year show that tuition and fees started to rise much faster for non-resident students at Illinois state schools when the law took effect.

University of Illinois spokesman Tom Hardy says the school would like to see the law repealed.