You don't want his attention. You want to find out how to meet his needs so that he can behave himself. He would if he could, so the goal is to find a way to help him. Typical dicipline is not going to be effective with him, you both need theraputic intervention to get you on the right path.
If you have not had a full evaluation from a Developmental Pediatrician yet, get an appointment. You will find them at your nearest childrens hospital. They will give you a full picture of your child's processing functions and what his needs are. It may take some time to get in, but it will be worth it. You will also have a full treatment plan from the Developmental Pediatricain, but for right now, you can put him into some therapy based on his symptoms that will help him.
You should be seeing a psychiatrist for medical treatment, and to case manage for you. See if you can find a board certified child psychiatrist. You should find a play therapist and a cognative behavioral therapist and ask them about social skills classes as he makes progress. If he has any language issues, seek out a speech therapy evaluation and get therapy. If he has sensory issues, see an occupational therapist. If he has fine motor issues, ask your occupational therapist to refer you to a developmental optomitrist who will check his eye muscles and his occular motor and visual motor skills. Seek treatment if he needs it.
Next, and entirely seperately from the private evaluations and therapy, write a letter to your school district and request a full evaluation of your son because you suspect that he has a disablity. Tell them in your letter that you expect to have a response from then within ten school days of the receipt of the letter. Always write to the school district, if it does not happen in writing, it never happened, so don't call. They will have 30 school days from the date that you sign a consent form agreeing to evaluate him. I suspect that if he is having the kinds of issues you describe, he may qualify for preschool services through your school district. This is a long process, so get started now. Read about advocacy at www.wrightslaw.com. Read about identification and what a full evaluation should consist of (called an MFE) You will want to be sure that what you consent to is a full evaluation and not a "screen" or a partial evaluation.
You should know that every teacher, even one with experience, is not cut out to deal with issues like your son has, espcially if he is not receiving therapy and is not getting school based interventions based on his pschological, intelectual, and procesing skill he data.
He does not want to be bad. He has a medical condition. He cannot count on his brain to fuction the way you do, or I do. Brain cells do not touch. There are very tiny spaces between them, called a synapes. Our thoughts are carried through the brain as electrical impulses, and when they reach the space, our body makes chemicals, called nuerotransmitters, that carry the electrical impulse to the next cell. If your son does not make enough neurotransmitter, or if his neurotransmitter receptors are damaged or malfunction, he has ADHD and cannot count on his throught process skills like you can. Every one has this issue to some degree ocasionally, like when you are standing in the kitchen and cannot remember what you went in there to get. Imagine that happening over, and over agian for the simplest of tasks, like knowing that he should pick up and go with the class, but he does not want to, and he can't process the information in his memory that will reason with him to stop the impulse to stay and do what he wants. Or, he knows (somewhere in his brain) that he should not hit, but he has an impulse, and he cannot retreive that infomation quickly enough to stop the impulse or it gets stuck along the way. Think how confusing life is for him, he cannot count on his brain to help him, and he does not know how to make the neurotransmitters to work any better. This is why medications help ADHD, and they do not make them zombies, or guinea pigs, or change thier personalities. You will need to be discussing medical treatment with a child psychiatrist and because of his age, he may not have all the treatment options available to him, but he can be helped. Medication is a tool, and should be used to help him make more progress in therapy.
I hope that you find some help, there is plenty out there to be had, so get moving, and give yourself a break too. Being a primary care giver is the hardest job you will ever do, so if you think you need help, get it. Always take care of yourself, most of us will need to seek some psychological care at some point in the journey, and there is no shame in it. You will be more effective if you take care of you.
M.