Witches of 1941

From the introduction:

You are witches and warlocks in training to use your magic to thwart the Nazi menace for the benefit of the British war effort. Your headmaster, Emelius Brown, is your only guide and contact to the mystical word, though he isn't much help. Turns out he made the whole course up based on an old book he found. Nevertheless, England needs your help. Use what little magic you have learned and defeat the Nazis!