Write the disruptive child's name on a large piece of poster board, and have him decorate the top 1/3 of the board with marking pens. Place the decorated board in a highly visible location in the classroom.
Tell the child that for each assignment completed, or for each followed instruction, he will receive a single sticker on his reward chart. Inform the child that when he reaches 20 stickers, he will win a prize. Show your student the various prizes he can win then place the items in a locked drawer.
Remind the child at the start of each new assignment, or at the beginning of each new instruction, that he can earn a sticker for following through on the task. As soon as the child performs the positive behavior, place a single sticker on the reward chart. Praise the child, and encourage him to keep earning more stickers by making good choices.
Give the student a choice of prizes as soon as he earns 20 stickers on his chart. Make a big deal of his achievement to reinforce the concept that positive actions have positive consequences. Help the child make a brand new chart, and repeat the entire process.