Rubber: You can eliminate the pencil marks by using rubber of good quality (Ex: gum erasers). Make sure you scrub the surface slowly and gently, or else the rubber will start to remove the paint from the walls.
Baking soda and Water Paste: Baking soda is one of the most effective cleaning agents widely used to remove all types of stains from different surfaces. Prepare a solution using baking soda and water. Then dip a cloth in the solution and wring it. Use it to rub away the pencil marks.
Toothpaste: Your white toothpaste is one of the best ways to clean the walls properly. Apply a thin layer of toothpaste on a clean and soft cloth. Then rub it gently on the affected spot and remove the stains from the walls.
Detergent: To remove pencil marks, you can also use a mild detergent. Take a soft, clean cloth and dip it into the mixture of detergent and water. Wring it properly and rub the spot gently. Always use a gentle detergent to ensure the paint doesn’t come off.
Spray the stained area with All Purpose cleaner and wipe with paper towels.
If stain persists, dampen a sponge with warm water and liquid dish soap to work the area in a circular motion. Rinse with water. Dry the area with paper towels. Repeat as needed.
From CrayolaFrom Bond Cleaning
I found a couple of suggestions online: