If it happens mostly in school.....the Occupational Therapist (OT) gave us some thick tubing, that we cut and put at the back of his pen and pencils....you let a piece stick out past the end of the pencil, so they can chew to hearts delight! You can buy the tubing even at fish shops, but what I didnt like about it, it has latex in it....but it worked. He was also allowed to chew thick gum in school.....at home he also used the gum. You can also order chewelery on the internet, or sensory jewelery.....Another thing you can teach him: Let him put the soft part of his thumb in his mounth , with the soft part showing upwards, like thumb sucking......then press gently but firmly onto his upper part of the inner mouth, the part above the tongue.....This will give him some relaxing deep pressure in his mouth.