The US is #1

The United States has the highest number... BBC News - Lack of sleep blights pupils' education

The international comparison, carried out by Boston College, found the United States to have the highest number of sleep-deprived students, with 73% of 9 and 10-year-olds and 80% of 13 and 14-year-olds identified by their teachers as being adversely affected.
In literacy tests there were 76% of 9 and 10-year-olds lacking sleep.
This was much higher than the international average of 47% of primary pupils needing more sleep and 57% among the secondary age group...
So the tests were accompanied by questionnaires for teachers, pupils and parents about sleep patterns. And this information was compared with pupils' test results, so that the performance in maths, science and literacy could be compared with levels of sleep.
.... "Our data show that across countries internationally, on average, children who have more sleep achieve higher in maths, science and reading."

Well, maybe the school can't fix it. Or maybe school should simply start later. (A practical problem for parents getting off to work, though.) Or maybe every day should begin with a YogaNap class. It would be interesting to see what happened to test scores.
Or then again, maybe not.