Cheri,
First, I am sorry to hear about what happened to your son...no child deserves that from bullies. I know I'm often here defending officers, but in this case, I would disagree (to an extent) how the officer handled it.
In Maryland, I can charge a 9 year old with assault. Your state might be different...and it may not be the officer
refusing to charge, but it could be that he
cannot make the charge. I do not know off the top of my head what Ohio law says in regards to assaults and how young an offender can be to be arrested, but I did find something in an article:
But in 2002, Ohio also toughened laws for serious youthful offenders and lowered the age to 10 that juveniles could be detained in state and county treatment facilities. It was the first new law addressing juvenile offender issues in nearly three decades.
If that law still stands, and assault means incarceration in your state, then that means the 9 year old would be too young to be detained (not meaning charged, but detained). I do not know what the mininum age is in your state.
Again, it could be that the officer cannot charge him, and as much as we would like to, we can't lock everyone up because we think they should go to jail...but a matter of what the law says. If the law says I arrest for it, then I arrest. If the law says I cannot arrest, then I cannot arrest. (for example, in Maryland, I cannot arrest for a 2nd degree assault if it did not occur in my presence...meaning if you are hanging out and a neigbor punches you in the face and you call the police...by law I cannot arrest. More on that in a moment).
Now, there are probably more options available to you. Do you have a DJJ (Department of Juvenile Services)? This isn't like social workers checking the welfare of the children, house, etc...it is the legal system for juveniles..much like our Adult court system. You may have the option to go to DJJ (or whatever your agency is) and take out the charges yourself. You could also talk to your courthouse to see about taking the charges out there. I cannot answer for Ohio law so I do not know what your procedures are.
In Maryland, an adult cannot take out charges against a juvenile..the police have to do it. If you were in Maryland, I would have arrested the kid with no problem. I make the arrest based on your statements about what occurred. In Maryland, a person cannot go to the courthouse to take out charges against a juvenile (only for adults), but it can be done through our DJJ system.
There are some flaws with our system though. For example, I do agree that kids to fight and sometimes get hurt...kids have not changed in hundreds of years and probably will never change...BUT Today I received a call for a fight in progress on a street in our projects. I get there and its a bunch of juveniles that had been fighting (broke up when they heard my sirens). I talk to the kids and I talk to the parents...I say 'Do you want them charged?' and they say Yes. I go around the circle and everyone says yes. Do you know what this means? It means that today I had to arrest 5 juveniles aged 11 to 14 who were all in a mutual fight...nobody injured. Then moms start asking "why are you charging my kid..." and I explain that the other kid wants to take out charges...so everyone is getting locked up. This situation is much different than yours, and I only mention it to give you an example of how Maryland law is set up. 2 kids fight, either both go to jail for assault or neither do.
I'm sure you have more options available to you... I would start with contacting juvenile services or whatever your local agency is.
One thing that I think you should consider also is talking to management at your apartment complex. If you are in an apartment, then I assume you are renting/leasing. Oftentimes, things like this are against the lease. Go to managment there and tell them what happened (not just with your son but the other incidents). They may not kick them out now but at least you get the process starting and when more people complain, something will be done.
I gotta get off line now, I'll talk to you all later. 
What about the bully boy walks nearby ur apartment does ur sons suppose to move away from him, like u said the bully boy has told other boys false story, huh? seems like cops didnt tell the bully boy not to play around ur son, but the bully boy was able to walk to talk nearby ur apartment with other boys :shakehead: