Reading good, quality literature is one sure way to help your child become a better student by boosting their exposure to well-written, masterfully-crafted sentences by classic authors. These books can also help reinforce exceptional character traits. Talk about what the characters in the story do to be kind, or how a certain character might have acted in a better way. Discussion, not just reading, builds better comprehension and allows for excellent analysis of behavior skills.
Here’s just one of many lists out there, broken down by grade level: Charlotte Mason book list.