Almost one in five public high schools have mandatory drug-testing policies, despite numerous studies that have shown little evidence these programs are effective, The Washington Post reports.

Each school drug test costs about $24 each, according to the American Academy of Pediatrics (AAP). Last month, the group announced its opposition to random drug testing in schools. There is little evidence such “suspicionless” testing is effective, and it comes with potential risks, the AAP said in a policy statement.

“Pediatricians support the development of effective substance abuse services in schools, along with appropriate referral policies in place for adolescents struggling with substance abuse disorders,” the group wrote.

In 2002, the U.S. Supreme Court ruled it is constitutional to test students who participate in extracurricular activities. The practice “is a reasonably effective means of addressing the school district’s legitimate concerns in preventing, deterring and detecting drug use,” Justice Clarence Thomas wrote for the 5-4 majority.

One nationally representative survey of 1,300 school districts found among those with drug-testing programs, 28 percent randomly tested all students. Schools in Ohio, New Jersey, South Carolina, Alabama, and Wyoming are currently considering mandatory drug testing programs, according to the newspaper.

A number of studies have questioned the effectiveness of drug-testing programs in schools. One of the biggest issues with drug testing is that it does not test for alcohol, the substance most likely to be used by high school students, the article notes.

The negative consequences of random drug testing include deterioration in the student-school relationship, potential breaches in the confidentiality of students’ medical records, and mistakes in interpreting drug tests that can result in false-positive results, the AAP noted.