Question: If I get rejected by my Early Decision I school in mid-December, am I allowed to apply to a different a school via Early Decision II in January? Thank you for your help.
Yes, if you have been denied in the ED I round, you are free to apply to an ED II college. In fact, even if you are deferred in the ED I round, you can still pursue another college via ED II, if you so choose. A growing number of seniors who are discouraged by ED I deferrals are choosing to try for ED II at a different school with the hope that the ED admissions-odds boost will help their chances. See this previous Ask the Dean column on what I call the "ED I, ED II ... Skidoo" http://www.collegeconfidential.com/dean/ed-i-ed-ii-skidoo
Note, however, that if you are deferred via ED I and then you apply elsewhere via ED II and are admitted, you can't wait until the spring to see if your ED I school says yes after all. You must matriculate at your ED II college (assuming that finances permit).