There's more biggest late elementary boys you can choose from, or if you want to write your own selection, pick the bottom most option:
Jake, age 10
Weight: 410 lbs
Build: All round
Notable features: Dark blonde hair, blue eyes, and peach skin
Other Notes: Had to stay with his aunt, while his parents are away on the business trip abroad. All that weight he had gained came from his aunt's delicious food, which coincidentally, she's the dinner lady at his school!
Lewis, age 9
Weight: 450 lbs
Build: Bottom heavy
Notable features: Brown hair, brown eyes, and peach skin
Other Notes: Arrives at his new school, after moving away from town. He looks so nervous about how the students would react to his enormous size for the first time, and hopefully he gets to have some friends with someone that admires his size.
Dean, age 11
Weight: 395 lbs
Build: Slightly bottom heavy
Notable features: Brown hair, hazel eyes, and pale skin
Other Notes: Dean had gotten so big, thanks to the feeding his girlfriend, named Kelsey, who finds him attractive when he eats and gains so much weight. Even when Dean was a little bit chubby the first time he met Kelsey, and she would normally invite him for dinner after school, so that she can spend a lot more time with him and his massive girth.
Kieran, age 10
Weight: 375 lbs
Build: Slightly Top heavy
Notable features: Brown hair, blue eyes, and peach skin
Other Notes: Kieran is hopeful to become a lineman for school football sometime soon. He may be the biggest they have, but to him it feels like he's not big enough, and tries to be the most standout out of not just the opponents, but his teammates too!