About a fifth of American 15-year-olds scored so low on the PISA test that it appeared they had not mastered reading skills expected of a 10-year-old"

https://www.nytimes.com/2019/12/03/us/us-students-international-test-scores.html 

"About a fifth of American 15-year-olds scored so low on the PISA test that it appeared they had not mastered reading skills expected of a 10-year-old"

 American 15-year-olds scored so low on the PISA test that it appeared they had not mastered reading skills expected of a 10-year-old"