The Seventh Gate  by Ameripuff

The Seventh Gate combines marvelous storytelling with a non-stop pace, full of wonderfully imaginative details.  It is set in an American school of magic (not the famous Ilvermorney) in Pennsylvania with its origins in the American colonial period (1720), and it bears little resemblance to the well-known school located in Scotland.  It is Drew's own elaborate and unique invention.

We follow the experience of 13-year-old Willow Carter and four other new students at Magus Academy as they face a daunting first year at the school and the inexplicable loss of their magic powers until they uncover the school's dark connection with the fate of the Susquehannocks, a tribe of American Indians who were annihilated in 1763 by white settlers who wanted their land. 

The students and faculty members are all well characterized, each with his or her own unique personality, each with strengths and weaknesses, with noble bravery and feet of clay.  Still, it is heartwarming to see how these five students--Willow, Lola, Lex, Sid, and Incheon--stick together during the difficult, disheartening year at Magus Academy, ultimately to form a new House, the Pathfinders, with its origins in the earliest days of the school's history.

I read the 122,000+ words in two nights.  It was a can't-put-it-down story.  Drew has written a sequel, The Prophecy, which is equally as imaginative (where does he get these ideas?) and which lends itself to the expectation of a third story sometime in the future.