This is a tough lesson to learn, no doubt. See, you signed a legal document stating that you would rent this place for x amount of time. You do have a way out of the lease, but your refuse to find another tenant because of your lame excuses. There are MANY ways to advertise a rental: the newspaper, Craigslist.com, the school's web site or other affiliated school media account and, of course, facebook.
So, you need to be an adult and do what you can to advertise this rental. Your excuses are not acceptable and just a cop out. You signed that lease and now you need to be responsible.
You do realize that the landlord has to PAY for his property and now you have left and stopped paying him. That is not fair for him and it is incredibly selfish of you to put him in the position of not being able to collect rent.
So, do the morally correct thing and sublet the space so the landlord can be paid for his rental unit.
You are in COLLEGE, not kindergarten.