Plano ISD officials are warning parents about a dangerous game that some students may be playing.
Students playing the "fainting game" are intentionally cutting off their oxygen supply for a temporary high.
The game could result in brain damage, seizures, stroke and even death.
In a letter sent home to parents, the district says parents should look for frequent headaches, broken blood vessels in the eyes, and marks on the neck.
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The district says children who play the "fainting game" are typically between 9 and 16 years old and are motivated by curiosity, not depression or anger.
The district didn't say if a specific incident prompted the letter.