I hadn't previously heard of this (I wasn't reading much YA stuff when it came out in 1983), but it's the first book in a series of books featuring two aspiring young wizards, Nita and Kit.
Matt de la Peña, the most recent author to win the Newbery medal (and the first Hispanic writer to do so) recently asked "Where's the African-American Harry Potter or the Mexican Katniss?" ( http://www.cnn.com/---/young-adult-books-diversity-identity ). Growing up, I was never particularly bothered by the lack of diversity in the YA books I read, but I did appreciate books with a non-white protagonist (like "Farewell to Manzanar"), so I do see de la Peña's point, and would be happy to see more diversity in the literature.
On the other hand, in this first book, Nita (Juanita Callahan) is the primary focus, but Kit (Christopher Rodriguez) shares all of her adventures and he speaks Spanish, so there's at least one Hispanic wizard out there - and there are at least 10 books in this series. Kit may not be Harry Potter (or even Ron Weasley) but he can do magic with an Edsel antenna and tame feral cars....
(I was looking up information on a favorite author, Mira Grant/Seanan McGuire, and she is apparently going to be a guest at the first Young Wizards convention...so I had to find out what the Young Wizards are all about!)