Sustained silent reading (SSR) is a form of school-based recreational reading, or free voluntary reading, where students read silently in a designated period every day, with the underlying assumption being that students learn to read by reading constantly. While classroom implementation of SSR is fairly widespread, some detractors note that the data showcasing SSR’s effectiveness is shaky at best and that SSR alone does not craft proficient readers. Despite this, many maintain that successful models of SSR typically allow students to select their own books and do not require testing for comprehension or book reports. Schools have implemented SSR under a variety of names, such as "Drop Everything and Read (DEAR)", "Free Uninterrupted Reading (FUR)", or "Uninterrupted sustained silent reading (USSR)". Value of Sustained silent reading Advocates' perspective According to advocates such as educational researcher Stephen Krashen, SSR has been shown to lead to gains in several literacy domains. Krashen looked at a large number of studies to see what conclusions were supported by empirical evidence. He found that concerning reading comprehension, SSR is successful; 51 of 54 studies found that students in an SSR program scored as well as, or better than, other students in this regard. It is most successful when used for longer periods. Furthermore, SSR was shown to create a reading habit. Several years after participating in a program, students reported more reading. One study found that a single SSR session was enough to change attitudes about reading. Long-term effects of SSR include better vocabularies, better writing skills, better spelling, and greater knowledge of literature, science, and "practical knowledge". Several studies noted that children in poor neighborhoods had less access to books at home and in libraries, and often the books available to them were not books that they wanted to read. Prize-winning books were often not especially popular with children. Comic books, on the other hand, are often not available in libraries but are popular with many boys, and reading comics was found to increase the reading of other books. Three additional studies showed that providing rewards for reading did not improve reading development. Krashen believes this is because the presence of a reward suggests that an activity is work, and makes it less appealing. In two other studies, teachers noted fewer discipline problems when an SSR program was being used. Detractors’ perspective While many critics note that SSR is beneficial to students because it