Hair testing of students is becoming increasingly popular in US high schools. The biggest company is called Psychemedics Corp, whose technicians comb through 80 schools in 26 states, plucking hair from students for laboratory liquification and analysis. Most of these schools are private, but the practice is becoming increasingly popular among public schools as well.
Hair grows about a half-inch a month, so the inch-and-a-half sample supposedly detects for drug use within the last 90 days. Some researchers claim that the tests cannot determine between external contamination and actual use, but Psychemedics claims they wash each hair to remove such a possibility.
Courts have upheld urine tests of school athletes in Oregon, and of students engaged in any extracurricular activities in Indiana and Arkansas.