The authors themselves admit that NCLB was a mixed bag: "Specifically, we find that NCLB generated large and broad gains in the math achievement of 4th and (to

The authors themselves admit that NCLB was a mixed bag: "Specifically, we find that NCLB generated large and broad gains in the math achievement of 4th and (to a somewhat lesser extent) 8th graders. However, our results suggest that NCLB had no impact on reading achievement for 4th or 8th graders." You'd think that you can employ drill practice to improve results in mathematics, but that approach won't work in English. American math instruction feels quite alien for foreigners, the emphasis is on the application of algorithms, not on understanding why and how they work. Equipped with plenty drill practice, an Amarican child can fill in the correct bubble on the test, no matter if or not it understands mathematics. Any understanding of mathematics gained in that system is purely incidental. That's all a hypothesis and would require further testing.