Frustrated parents are us

I have two children who live with me and my wife. One daughter who is 12 turning 13 soon and one son who is 9 working on 10. I seriously doubt that either one of them are going to make it to the next year. LOL... KWIM??
No matter what I do or say my children have decided that they are going to do what they want. When they are confronted about this or that they lie about it. For instance, last night my wife and I come home from date night and I know that someone was sitting at my desk because the keyboard to the computer and the phone are all out of place. I asked them why they could not keep things in their place when sitting at my desk and they both begin to lie about not having been anywhere near my desk. I wanted to kill them both. Why are they lying about such a simple thing. I told them that I did not care about them using the computer because they both have been using it with our permission. However I do expect them to leave my area the way they found it and not messed up. I dont think that is an unreasonable expectation.
The other day Katy, my wife goes outside and calls the children. They are no where to be found. We start calling the neighbors and find out they are across the street in her house. We get the children back home and we tell them for the one millionth time that they are NOT supposed to go into someone's home without asking our permission and letting us know where they are going to be at all times. Our expectation is that we will know where they are at so that we can be aware of what is going on at all times. For whatever reasons our kids just do not seem to care what we say.
I have tried everything that I know to try to communicate to the children that obedience is expected. They know that they know that if they insist on lying to me or their mother that they will be punished. I know that I am not alone in these struggles. How do you deal with lying and outright disobedience? I told my wife the other day that I need to get a prescription for Prozac or something that will just keep me happy all the time and not care about what is going on anymore. It would be so much easier for me to be like a lot of parents that I see that just ignore what the kids are doing and let them just have a free reign in the home. However, I just can not tolerate their decision to just do what they want despite our having set up simple rules and expectations here in our home.
Our desire is that our children will grow up to be responsible, God fearing (respectful), obedient, productive members of society. I think that every parent desires this and that we are not alone. We ask our children to do chores around the home like most parents. One reason is so that they can learn responsibility and another is so that they can contribute some help to our family unit since we both work three jobs between the two of us. Why do we constantly have to stay on them to get them to do the simplest of tasks?