My gpa was an 85% in my third year. However, a friend of mine got in with a 78% average a few years back (but do your best to aim higher in case there are a lot of applicants in your year). They'll look at your third year marks if you apply while you're completing your fourth year (which i did) since those are the marks available. If you apply after graduating, they will look at your fourth year marks. They also tally up marks from earlier years when it comes to your teachables, since you need 6-full year credits in your first teachable and 3- full year credits in your second teachable (they'll choose your highest marks in each teachable). I hope that makes sense!
Once you get your acceptance, they just want you to keep a mid B average However, I was told by someone on the decisions board that your experience, statement of intent, and letters of recommendation matter much more because that is where they are able to get insight regarding how committed you are to teaching/ being an educator.