I would say yes and no. Outside of kids who really do better on lower carb--kids with seizures, diabetes, etc.--the fact that their glucose-consuming brains are such a larger part of their metabolism probably does give them a bit of a buffer versus sugar compared to adults. In terms of toxin, that just makes for a higher dose of sugar needed to do damage. But that big glucose consuming brain's liable to also be why they have a higher liking for sugar, which makes them more likely to hit even that higher toxic dose. And going through development, bone growth, puberty etc. at those toxic levels, and with the higher chance of deficiencies in various vitamins and minerals that goes with a higher processed, sugary diet is not a good idea.