Gates' Met Project (my comments inline):
For students in grades 1 through 3, the improvement in mean reading scores between October and April were larger than differences between April of one grade and October of the subsequent grade. Because students generally spend more time in school between October and April than between April and October, such a finding implies youth are improving their reading comprehension more during the months when they are in school.
However, beginning in fourth grade, that is no longer true! The norm sample results imply that students improve their reading comprehension scores just as much (or more) between April and October as between October and April in the following grade. Scores may be rising as kids mature and get more practice outside of school. However, the above pattern implies that schooling itself may have little impact on standard reading comprehension assessments after 3rd grade (Is that really the best explanation they can think of?).
But literacy involves more than reading comprehension. As the Common Core State Standards recently adopted in many states remind us, it includes writing as well. (Who needs to be reminded, by the CCSS no less, that literacy includes writing? English teachers? No. Anyone who ever wrote or read a set of ELA standards? No. Normal humans? No. Legislators, wonks, and people at Gates? Apparently.) In fact, English teachers after grade 4 generally focus more on writing than teaching children to read. (Do they? If so, it is despite a decade of federal regulations and reforms pushing against it.). That is one of the reasons why we supplemented the state ELA tests by administering the Stanford 9 Open-Ended assessment, which provided students with reading passages and then asked students to provide written responses (Were these questions designed to evaluate reading and writing separately?). The implied standard deviation in teacher effects on that alternative assessment Stanford 9 performance was somewhat larger, in fact, than in math. In future analyses, we will be investigating whether teachers have a stronger influence on writing skills than they do on reading comprehension, by analyzing the writing prompts in some state assessments separately from the multiple choice reading comprehension questions (And really, who cares? What are you going to do about it?).
Gates real agenda in English is to figure out how to shape the discipline to be amenable to value-added assessment.