Hello A.,
Your post didn't give us much detail about what you've already tried so the suggestions you get might not be so helpful. I guess you held your son back in kidergarten because of maturity issues but were there also academic issues? I think you said your son was not doing his work and that is also a RED FLAG.
In general, kids need incentives to learn new skills and consequences when you know that they understand expectations but choose not to comply. As as Learaning Coach, I work with kids who are struggling in school and sometimes they have a Learning Difference. Many times their behavior at school was as the class clown or the bully because of undetected learning disabilities. In general, kids "act up" for a reason i.e. boredom, or a need to stimulate the brain as in ADHD, or a need to control others because he feels controlled by someone else etc.
It may be wise to try to discover the "why" behind the "what". Developmentally speaking, 7 year-olds like to please you and they care about what you think of them and thrive on praise (you notice them being well behaved and you point it out). Your child will know that you love him when you take the time to have a heart-to-heart (being calm and concerned) talk with him and try to find out why he is picking on kids. There is always a reason so don't take, "I don't know for an answer." He might tell you that he is angry and then you need to teach him acceptable ways to deal with his anger. You might find out that someone else is abusing him and he is acting out what he is experiencing. But you might find out that he feels badly about himself and he is using his brawn to cover up for feeling insecure and sad over finding the academic part of school a challenge.
With such limited information, the reader of this post doesn't know the extent of your son's bullying and it is difficult to say if the solution is a simple incentive chart to encourage positive bahavior, more formal anger management training or a further research to explore conduct disorder or oppositional deficit disorder.
Your post said, "I don't want to punish him and have him think I don't love him." Keep in mind that true discipline comes from the intent to teach and train in order to improve a skill or a behavior. A consequence for pushing a kid in line at school might be to write a note of apology to the student which teaches your son to admit that he did something wrong and take responsibility for his actions. Then he needs to do one nice thing for that kid to experience what "kind" behavior feels like. In my opinion, that is love.
From www.helpforreading.blogspot.com