Steven Butnik’s article Understanding, Diagnosing, and Coping with Slow Processing Speed.
Consider whether the student is being held back by anxiety, a learning disability that is making the content difficult to process, a condition like dysgraphia that makes handwriting especially challenging, eyesight issues that make the board or papers hard to read, or auditory processing difficulties that make working in a busy, noisy classroom very difficult.

In The Power of Validation, Karyn Hall and Melissa Cook define validation as “the recognition and acceptance that your child has feelings and thoughts that are true and real to him regardless of logic or whether it makes sense to anyone else.”

Students who frequently get stuck on school work may lack the problem-solving skills they need to get unstuck. So whenever you can, model your own strategies with teacher think-alouds, and get other students to do the same thing.

Michael Dunlea finds that in many cases students get hung up on one specific aspect of an assignment, so if he is able to figure out what’s confusing them, he can help them continue.

For some people, simply setting a time limit for a task is enough to get them moving more quickly, so it’s worth a try with your slow-paced students. Use this one carefully, though: For some students, it could cause even more anxiety and make them shut down completely.

Break Large Tasks into Small Ones

Offer a “Can Do” and a “Must Do”

Provide Estimated Times for Each Activity

WIRMI
Problem-Solving Strategies for Writing by Linda Flower.
“What I really mean is…” and continue in whatever language you would use if you were describing the idea to a friend.

Establish a Bare-Minimum Goal for Formative Assessment

Mix Low-Stakes with High-Stakes Tasks

Mark Problem Items for Later: instructional coach Gretchen Schultek Bridgers advises students who get stuck on an item, especially on a test, to mark it with a small post-it note, a highlighter, or a star as a reminder to come back to the item later. This kind of strategy will be useful to everyone, not just your slow working students.