Not sure a HL 25" long racket would have the necessary mass to get a ball over the net from the baseline. I'd try to calculate the SW and see what kind of number you come up with before trying to get a HL racket.
I've just had a quick measure and my daughter's 25" Head Gravity jr (the one with the same colour way as the adult ones, rather than the cheaper one) is exactly at 317mm with a (pink) overgrip on and the dampener off.
@Steve Huff is right. 25” rackets are going to be light rackets and an even balance for an 8 oz would be 31.75 cm. That means the inertia (SW) added for the 10 cm axis would only be about 106 SW points. And you add that to the rackets inertia at the balance point or RW To get SW. With a light weight racket the balance will need to be high to create a longer distance between the SW axis and balance point to get any plow through. You do not want a head light racket because the total weight would need to be much higher to get enough plow through.
OTOH adding weight to the grip of a 25” racket would raise the total weight and balance with little or no change to SW. even is all you add is an OG. So if you want a HL racket and your junior can handle the extra weight go for it.