You cannot be told you cannot homeschool your children - its against the law. If you are certified and/or can get certification to homeschool - you are ALLOWED to homeschool and no one can stop you. I dont understand this because you said you homeschooled before - were you not following the rules for homeschooling? Is that why they said no now?
If you kept your son out of school without reason, then yes, the school had legal rights to do what they did. I can understand you having surgery, but you have a legal obligation to have your son attend school, either through homeschooling or have someone else get him there. A doctors note is the only excused absense, short of a funeral and/or court. Here it is 9 days as well and if after 9 days are missed, regardless of excused abscenses or not - you must go in front of the School Board and explain - or your child fails the grade. I think its that way everywhere now a days.
Children shouldnt be hitting each other - and while that girl had no right to hit your son, your son shouldnt be hitting a girl - ever. What does that teach him in the long run? Too many kids are learning to use their fists instead of their words - thats the problem. I do believe in standing up for yourself, absolutely - but at 7 years old I think its taking it a bit far to hit - on either side. Sit down and talk about things.... if later on in school (middle /high) some one keeps it up and after repeatedly picking and it doesnt stop and throws the first punch - then... you hit back and only as a last resort. That is how my kids were taught and thankfully, have never had to resort to that and they are 10 and 18. I dont condone violence, but... sometimes its necessary when every other means fails and you are against the wall. Your son is by no means against a wall however I dont believe.
This school system sounds like its in trouble from the get go. Teachers that refuse to do anything, a principal that refuses to do anything...... I dont know - maybe its just me that views it like that, but - SOMEONE has to advocate and it doesnt sound like the school cares that much - its more like "get 'em in - get 'em out" type of situation. Thats awful - its elementary school - I can only imagine whate middle and high school has in store.
I'm so sorry you and your family has to endure this...