hello... my 11yr old was like that (but he was ultra skinny at that age and then spurted 6" in the first two months of first grade and packed on 20lbs (the best side effect he's ever had from a medication))
I would say yes, partly because (if he is like my son, even though MY son was leggy, he may outgrow the Regent at 6.5yrs old) he needs time to be used to a booster before he HAS to use one all the time.
And as for how you clothe a child like this... well, my trick was thrift stores... especially as HARD as Damian is on his clothes... when he was in his worst spurts, we weren't even able to save any... because literally the growing that fast made him so clumsy he was just ripping his clothes to shreds in the process.
Also, adjustable waist pants... and stashing a full wardrobe of pants in two different sizes in my attic (so when he was a size 8, we had sizes 10 and 12 in the attic... when later that year, he was a size 10, we stocked up on size 14... and you get the idea.
Now he likes his clothes super loose, though, so we don't have to... and his growth has slowed considerably... he's only going through a size a year for the past 2yrs... so the trick is to have the pants 2sizes bigger (like he likes) and then make him wear a belt... and of course, hemming without cutting... and hem in sections... so I can undo ONE hem when they're about ONE size too big... then undo the other when he no longer needs the belt.... and start buying pants again.
Shoes... he was going through them about every 6mo... so whenever his shoes grew, I started sale-hunting... even now that he (for the past 2yrs) is down to about 1 size a year, he wears his shoes hard... so I watch the sales close... and I watch the shoes for holes... I also buy shoes in 2s... when I bought his size 10s at the beginning of the year, I also bought size 11s. if he hasn't outgrown the 10s (the first time EVER that will happen.. him not outgrowing a size at the end of the summer), then I'll still hunt down a sale... because we have found ONE brand of shoe he doesn't wear through in 6months or less... Lands End... the really good moccasins (and he loves that they are slip-on) to order a size 11 in those and pack the regular sneakers away for his brother or let him have them as a backup pair
Oh... and he always has liked wearing shirts big... so I buy them so that they last through 2 sizes of pants...