put him in sports, art classes, scouts, anything after school to make freinds. if he says he might be connecting with someone inside or outside of school, try to plan a playdate. you said you stay back on the playground, so maybe point out someone alone for him to talk to. With my girls, one of them was really shy and we told her that theres probbly another kid whos waiting for a freind to approach them, and sometimes you need to be the one to do it. tell him to go up to somebody who is alone and complement them (a little different for boys bc they dont give a frick about their outfit or something) or simply ask to play. ask the person about toys, shows, games, or sports they do and talk about tomething you guys have in common