The choking game has surfaced at schools in southern Ontario again.

Parents across the Lambton-Kent District School Board are being told to look for signs of the dangerous "game" that deprives kids of oxygen and could lead to death.

Kids strangle each other or hold their breath to the brink of unconsciousness attempting to get a rush or high without the use of drugs.

A letter warning parents was recently sent home by the Lambton Kent District School Board. A fact sheet has also been posted on the board's website.

In Windsor-Essex, Stephen Fields of the Windsor-Essex Catholic District School Board, said there has been one incident in this region this school year.

He didn't offer many details but said three students were involved.

"Quite honestly, it's concerning to us because it is naturally a very risky behaviour. Kids can die doing something like this and as a system we care about our kids and certainly don't want them doing this kind of thing," he said. "Obviously, this is a teachable moment."

Windsor-based parenting expert Win Harwood said the kids most likely to try the choking game are between the ages of nine and 16. She said it's most dangerous when young people do it alone.

"Sometimes, we think that they don't need us as much as parents; they don't need our supervision. So we allow them to go to their room for long periods of time, but I think it's a mistake," Harwood said. "I think that we really need to know that our children still need us to check on them, to supervise. They need us to connect with them, and we need to know what they're doing on the internet as well."

Harwood said there are detailed how-to videos online that parents need to know about.