Age 14 is GoF and 13 is PoA, which story are you attempting to write this from? The ages confuse me to no end in regards to which you are writing this story from.
In PoA, Sirius Black is Harry's antagonist. So, 3rd year. Considering Hermione is a year older than everyone else (Her birthday is September 19, and she turned 14 when everyone is 13) I like to think that I followed the canon timeline pretty well. Other than the fact that Harry wasn't looking over his shoulder for Black.