FWIW, when I worked at a learning center, we would put kids diagnosed with one of these "learning disabilities" in their own room with a window looking out with an assignment they were prepared to do. They could doze off, doodle, go to the bookshelf for something to read, and then get back to the assignment.
Without exception, they worked out a pattern for themselves. Often, it was a short nap. This held for all age levels.