Increased speed isn't *supposed* to happen at early ages. The design, the internal files, and the ingame lessons all point out for vampires to gain their powers at YA, which includes a moderate bonus to skilling at night.
There is, however, some big bugs in the skill-gain system in the last patch. "Starship Troopers"-sized bugs. These bugs result in the somewhat benign effect of supermanesque learning for vampire kids from toddler to child (possibly teen as well)... and they result in the not so benign effect of sims randomly becoming unable to raise skills anymore. Luckily, the latter is rare.