There are, according to the article, 16,000 primary schools in the country and 602 teachers completed the report. I can't see that that is anywhere near a big enough sample for the conclusions that are being drawn. If there are just 5 teachers in each school, that equates to 0.75% have replied. Not that 0.75% have a problem with this, but that 0.75% have replied. Nowhere does it say how many people have actually reported the problem, just that they've found some examples in what they call 'a substantial number' of schools. How many is that? 5? 50? 500? Without that number there is no way that anybody can judge whether this is a serious problem or merely an isolated instance.
Shoddy journalism.