How should I punish my 7 year old son?

I am a proud mother of my 7 year old boy. He means everything to be but his behavior has been concerning me. His teacher keeps calling me saying that he constantly disrupts the class and gets out of his seat. About one month ago, my son got suspended for throwing a tape dispenser at another girl. While I was doing grocery shopping, his teacher called my cell telling me to pick him up. We had a meeting with my son's homeroom teacher, the principal, and the girl's parents. Her parents took her to the doctor to make sure she was OK. I grounded my son for a week and he was not allowed to use electronics for one week (including TV and computer). He also had to write an apology letter to the girl and her parents. My son had a problem with throwing things before this incident. This night at 3:00 AM, the police knocked on my door stating my son spray painted a few neighbors' cars. I had to stay in his room all night to make sure he doesn't sneak out and I'm tired because of this. I looked at a few of the neighbors cars and they were covered in spray paint. I asked my son where did he got the spray paint and he said he took it from the neighbor's garage. I don't know how to punish my son. Are there any parents that can help me?