The lessons aim to help children learn more effectively, be calmer and enjoy better mental health.
They teach pupils about the importance of getting at least nine hours' shut-eye a night and avoiding taking gadgets such as mobile phones, laptops and games consoles under the covers with them.
Although experts say pupils should be sleeping for more than nine hours a night, some get as little as four.
The charity Sleep Scotland, which is running the lessons, says sleep deprivation makes children too tired to concentrate because their brains can't work to full capacity.
"You wouldn't send somebody to school without having the right amount of food, so why would you send them without enough sleep," said director Jane Ansell.
The charity is urging the Scottish government to extend the trial from the current four schools.
