How many students struggle as readers? What percentage of students in the United States are behind in reading?

The National Assessment of Educational Progress (NAEP), first administered in 1969, is the largest continuing and nationally representative assessment of what our nation’s students know and can do in subjects such as mathematics, reading, science, and writing.
Students in grades four and eight are tested every other year. According to the most recent report released in late 2019, 35% of all students read below the basic level which represents a 2% increase from 2017. More troubling is the fact that while score’s of the highest-achieving students have increased in reading, the scores of the lowest-performing students have decreased. More than half of Black male students were tested at below basic, and just 10 percent were proficient. The chances of a Black male student being taught to read well is close to one-fifth that of a White female student and one-third that of a White male student. Nationally, the percentage of Black students reading at grade level is only two-thirds that of White students. “The top is going up and the bottom is going down, with the bottom dropping a little faster,” said Peggy Carr, from the National Center for Education Statistics.
The most recent study of adult literacy in the United States was published by the National Assessment of Adult Literacy (NAAL) in 2003 and is a nationally representative assessment of English literacy among American adults age 16 and older. Sponsored by the National Center for Education Statistics (NCES), NAAL is the nation’s most comprehensive measure of adult literacy. Over 19,000 adults participated in the national and state-level assessments, representing the entire population of U.S. adults who are age 16 and older.
The report concluded that 30 million adults — 14 percent of adults (over age 16) are functionally illiterate and that another 63 million adults — 29 percent of adults don’t read well enough to understand a newspaper story written at an eighth grade level. Among the over 200 million adults (age 25+) in the United States in 2010 approximately 15% have NOT earned a high school diploma or an equivalent degree (American Community Survey).
Obviously the number of struggling readers spanning in ages from early elementary grades through adults is vast. The question then becomes how is it possible that a nation that has spent more money on reading education than any other nation in recorded history has such a high percentage of its citizenry perform so dismally in reading?