My credit score is 660. Good or bad?

I got rejected for a Sears Card. I went online to check my credit report and it came back 660. Should I have gotten rejected?
Update: Okay, so the general consensus is that I'm barely average. How can I boost it up to say 700 within eight months. How about 720 within a year? Just some additional info, I'm 23, have student loans, and am still in grad school for another year making very little money. According to my credit report I have... show more Okay, so the general consensus is that I'm barely average. How can I boost it up to say 700 within eight months. How about 720 within a year?

Just some additional info, I'm 23, have student loans, and am still in grad school for another year making very little money. According to my credit report I have 8 accounts in good standing but one account where I was 30 days overdue (they kept mailing the bills to my old address) Impossible?