How much magic can children do before they go to school?
The main condition for getting into Hogwarts is that you have the ability to produce magic. Obviously, children don’t use a wand until they attend wizarding school – so this magic is not controlled. Instead, young witches and wizards will demonstrate they are magical by doing something accidentally, often when they are scared or angry.
Strange things happened to Harry before he attended Hogwarts, which he could not explain at the time. When Aunt Petunia gave him a terrible haircut, it grew back overnight. Another time when Aunt Petunia tried to force Harry into a horrible hand-me-down jumper, it shrank. And when Dudley and his gang chased Harry, he found himself out of their reach and up on the roof of the school. Finally, when Dudley thumped Harry in front of the snake in the reptile house at the zoo, the glass vanished. While Harry didn’t know it at the time, he was using his magic.
It’s not only children who are unaware of the wizarding world that do unintentional magic. In fact, Neville Longbottom’s family were so desperate for him to show any signs of magical ability they tried to force it out of him. He was pushed off Blackpool pier by his great-uncle Algie – though nothing magical happened then. He was also dropped out of a window by the same great-uncle. However, this time he bounced all the way down the garden and into the road, showing that he did have magical capabilities after all.
So, before children go to wizarding school, they do have magic – which seems to be driven by their emotions. Nevertheless, they don’t have a way to channel or control it, as they don’t have a magic wand.