The Witches of Willowmere

Sixteen-year-old Claire Norton refuses to believe in witchcraft. But when strange and terrifying things start happening in her school and community, she begins to wonder if there might be such a thing as magic... and whether she herself could possibly learn to wield it...

This is the first book of a trilogy. It's an older story, but new to this site. (Note: This story was originally set in the early Noughts, but has been updated to the present day.)