I can't get my Iphone 4 screen to work at all.

Today in school I was using it just fine. Until I noticed I couldn't slide to unlock it, or slide the up or down things. I can't even turn off. I tried looking up other things but the ''hard'' way of reseting the phone didn't work either and I tried many times...My phone is cracked, I guess somewhat bad. BUT before when it happened it worked perfectly fine for the past few months, I've also had this phone for a little longer than 2 Christmases, I never had any problems with it until today. I do have a password on my phone, and also ITUNES downloaded on my laptop. I can't restore it or anything because I can't unlock my phone, or connect it to the itunes thing on my phone because i cant turn it off to connect it to it.

I CANNOT do anything to turn it off, or slide the screen to unlock my phone. All it does is shows normally.

Someone, please help me!