Tell the truth and tell the school that they are your last choice, see how that goes...lol
You do not have to lie but you should kiss a little ass. Look into the school and tell them why you see their program as a great fit for you. Maybe there is some interesting research going on there, you like the location, you like the curriculum structure. Maybe you want to start fresh and you see the school as a good place to do that for so and so reasons. If it is a new school, maybe you like the idea of being part of something new and dynamic that you can help to mold and grow with. They feed you creative literature when they tell you how great their school is. Mix ass kissing with explaining to them why you would compliment their school and be a strong graduate.
Good Luck. Career centers on your campus are good at helping you be creative with these types of essays.