SAO PAULO (AP) — Grade-school students in a northeastern Brazilian city are using uniforms embedded with locator chips that help alert parents if they're cutting classes, the city's education secretary said Thursday.

Twenty thousand students in 25 of Vitoria da Conquista's 213 public schools started using T-shirts with chips earlier this week, secretary Coriolano Moraes said by telephone.

By 2013, all of the city's 43,000 public school students, aged 4 to 14, will be using the chip-embedded T-shirts, he added.

Radio frequency chips in "intelligent uniforms" let a computer know when children enter school and it sends a text message to their cell phones. Parents are also alerted if kids don't show up 20 minutes after classes begin with the following message: "Your child has still not arrived at school."

"We noticed that many parents would bring their children to school but would not see if they actually entered the building because they always left in a hurry to get to work on time," Moraes said in a telephone interview. "They would always be surprised when told of the number times their children skipped class.

After a student skips classes three times parents will be asked to explain the absences. If they fail to do so, the school may notify authorities, Moares said.

The city government invested $670,000 to design, test and make the microchipped T-shirts, he said.

The chips, similar to those used to track pets in many countries, are placed underneath each school's coat-of-arms or on one of the sleeves below a phrase that says: "Education does not transform the world. Education changes people and people transform the world."

The T-shirts, can be washed and ironed without damaging the chips, Moraes said adding that the chips have a "security system that makes tampering virtually impossible."

Moraes said that Vitoria da Conquista is the first city in Brazil "and maybe in the world" to use this system.

"I believe we may be setting a trend because we have received many requests from all over Brazil for information on how our system works," he said.