How and why did Feinstein High School's test scores in reading and writing go up so dramatically in just one year? The short answer is... test prep.
Prior to this year, the school was organized into multi-age groups with promotion based strictly on a standards-based assessment of student work in a portfolio/exhibition. Thus "11th grade" students weren't necessarily grouped together. Some would be with the "seniors," others with "freshmen" and "sophomores." This is not optimal for preparing for the 11th grade assessment, and for this as well as general philosophical reasons, the school did little direct test prep. Their overall approach to project-based learning also did not focus on the kind of tasks that turn up on the exam, particularly the reading exam.
This year, the school was turned back into a regular school like any other in the district by the Brady administration. This meant that all the now officially 11th grade students (how this was determined by the district might have also made this group stronger, btw) had English together. Oddly (and presumably to save money), the NECAP is given in October, which meant that the students from FHS taking the test had two years of interdisciplinary, project-based curriculum, followed by about six weeks of test prep. This, apparently, is a good combination. Don't expect it to be replicated, though.