I have a 10 year old foster child who can still wear size 6 shorts and t-shirts. Eventually he got a little taller but super-duper thin. We're FINALLY down to a size 8 this year, but before that we were a size 7. The Levis slim fit performance jeans are the only ones he'll wear because they're really skinny and he loves the soft fabric their performance line is made of consists . Even size 8 has big elastic bands that reduce the waist, which will help your slim kids. I've searched and searched for strong, slim jeans with regular boots/regular cuts (no skinny jeans) and this is the best I've found.
Spotted Zebra Boys' Stretch Denim Jeans by Amazon Brand
64 Review
Ultimate Comfort for Boys: Lee Performance Series Extreme Comfort Slim Fit Jean
41 Review
Classic Levi's Boys' 505 π Regular Fit Jeans for Everyday Wear
38 Review
π Essential Straight Fit Jeans for Boys: Top Choice in Amazon's Boys' Clothing Collection
47 Review
Waterproof Cozy-Dry Rain/Snow Pants for π§ Kids by JAN & JUL, with Fleece Lining
64 Review
π₯ Stay Warm and Active with Rocky Fleece Thermal Underwear Bottoms for Boys
44 Review
π Bold Pack Sleeve Active Hoodie Sweatshirt Set for Boys' Clothing - Stylish and Comfortable!
47 Review
π Boys' Outdoor Climbing Convertible Trousers - Waterproof | Clothing
47 Review