Problem child getting worse

my son is now 9 years old.  Lately he has been getting into more trouble at school.  For a while, his doctor had him on Stratera (Strattera), but since, that dr has left this area and he has gotten a new dr.  this dr has said that there is no need to have him on that.  There are times that i feel the same way.  He has lately gotten a very bad attitude at school and started lying and stealing.  He is disruptive at school, and lazy at home.  He has 3 younger siblings, very young, and he at times is mean to the oldest of the 3.  Today, he comes home from school and gives me a note from his teacher.  The note stated that he hid a note from her the day before, and that she needed to talk to me to set up a conference about his recent behavior.  When i went through his back and found a few sheets of paper stapled together that were sentences he had to write at school.  i found a sheet that was not finished, so i made him sit at home and write them.  The sentences were as follows:
I will not steal from the teacher.
I will not read books during class.
I will not hide notes from my mother.
I will not lie.
These are the current issues.  When i asked him why he hid the notes from me, he said he was afraid he would get into trouble. I asked, 'Do you not think you will get into more trouble by hiding them?". He said no. Grounding him does not seem to affect him, and we try not to spank unless absolutely needed.  I have gone through my mind over and over as to what we could do now, but me and his father are both out of ideas.
Here is a list of his living style:
We are a moderate income family, both parents are in the home, working mother, stay at home dad. He has 3 younger sisters, one is age 3 and there is a set of 2 yr old twins.(all girls).  He has a dog, and 3 cats.  We own our home and live in a very small rural area.  His school is so small, there is only one teacher per grade.  He has been disrespectful to all others, including me and his father, and he is rude and hateful toward his sisters.
Now that i have said all that, my question is: What can we do to adjust his behavior in a permanent way so that us as his parents can be able to modify his siblings as well?

[momtofourboys]

okay does he have anything like a play station or game boy or any kind of games what does he like to do? take that away from him and tell him he has to earn them back that these are extra fun things and when he can behave and respect and not lie he can earn them back when you feel is right. my friend did that to her 10 year old it took only one week to get his game boy back and she saw a makor change.
Another friend of mine her daughter was acting the same way (there are 5 girls in the family and my friend is now a single mom)
her middle daughter was acting this way but started beating all of her sisters up. she thought it had to due with kicking their dad out, come to find out Allie has allergies and for some reason it was causing this behavior. she is doing beeter now that mom has taken it away.she ahd to get rid of the allergy
good luck
Michelle