Sometimes scientific studies seem to offer some seriously "duh" findings.
At Big Think, Robert Montenegro links to a study by Scholastic that finds allowing kids a say in their own reading material can affect their reading proficiency. This is a result that, I think, is confirmed by every kid who ever lived.
Of course teachers have an interest in directing some of their students' reading -- they're supposed to be teaching, after all, and that means exposing students to things they don't already know so they can be learned. But the percentage of directed or required reading should probably not be the majority. The study says that when kids are allowed to read the things they like or want to read, they read more. And reading more helps them read better.
I've got a memory of third grade that suggests this is true. The one time I can remember ever being "sent out into the hall" was when I hid a book I wanted to read inside the book that we were supposed to be reading. Both were books of assigned reading, but for some reason one held my attention enough that I didn't switch to the other when we were told to. Did it make an impression? Well, the book we were supposed to be reading has vanished into the four decades of time that's elapsed since that dreadful punishment.
The other was a kids version of the Battle of Thermopylae. And when the teacher made me sit in the hall with the book, I read it twice and was on my third time when she called me back in. Go tell the Spartans indeed.