Now what?

So Izzak got home from school today and called me
Izzak: Mom can I have Top Ramen for lunch? (he got out early for early dismissal) Oh and I had In school suspension today. (in a tone as if it is a normal occurance)
Me: Uh what was that?
Izzak: Can I have top ramen? (not sure if he was trying that one)
Me: No the second part...
Izzak: I had in school suspension today.
Me: Why?
Izzak: I got in a fight... with "D"at school today, he hit me in the stomach and I got mad and started hitting back. When they pulled us apart they sent us to the principals office and I had to go to the ISS room today for the rest of the day.
Okay the problem here is "D" has been harassing Izzak physically and mentally for several weeks now, he has tried talking to teachers, the counselor and others but the only thing he has gotten from them was "ignore him he'll leave you alone" . Apparently this didn't work. I don't know does it every really? I mean it is one thing to say that between your own children but when the problem goes over several weeks and one such time involves my son feeling intimidated by this boy holding a pair of scissors when does it become something the school feels needs to be dealt with? It should be long before my son is worried about this kid and a pair of scissors! Apparently the school now thinks there is a problem with the boys only now that my son decides he has had enough and fights back. My big conern here is Izzak has had problems with bullies and just plain bad kids in the past and been able to handle it without fighting himself even though his dad has always told him if someone hit him and he defended himself by hitting back he would not be in trouble with us. Now that he has had the experience of fighting with another child other then the normal fighting with his brother have we turned a chapter? I really don't want my son to fight or have to fight for himself or anyone really. I spoke to the vice principal and he will talk to Izzak tomorrow as he wasn't there when it happened and has promised me he will try to get the boys seperated to different classes but I have heard this before and had lots of promises from the schools I feel like I am holding my breath now to see if anything will happen or will my son have to fight to defend himself again! He is only in the sixth grade now I don't want to worry about fights for the next 6 years, he has enough to deal with at school!