There are several options available to you.
The school can make up whatever rules it likes AS LONG AS IT DOES NOT VIOLATE THE LAW.
A disabled child cannot be punished for behaviors that are caused by their disability. The school is required to conduct a review to see that your child's rights are not being violated.
If the result is still not satisfactory, you are entitled to an impartial hearing.
The US Supreme Court has ruled that parents are partners in the IEP process, with veto powers to the changes chosen by the Committee on SpEd and the right to bring suit in US Courts to seek redress. They can employ an attorney OR file a complaint with the US Dept of Education's Office of Civil Rights. The OCR is empowered to investigate and pursue violations of federal Ed law.
Manifestation determination review.
If child with disability engages in behavior or breaks a rule or code of conduct that applies to nondisabled children and the school proposes to remove the child, the school must hold a hearing to determine if the child's behavior was caused by the disability.
http://www.wrightslaw.com/links/glossary.sped.legal.htm
Manifestation Determination
The IDEA requires that "within 10 school days of any decision to change the placement of a child with a disability because of a violation of a code of school conduct ..." the school, "the parent, and relevant members of the IEP Team shall review all relevant information in the student's file, including the child's IEP, any teacher observations, and any relevant information provided by the parents to determine -
(I) if the conduct in question was caused by, or had a direct and substantial relationship to the child's disability; or
(II) if the conduct in question was the direct result of the local educational agency's failure to implement the IEP.
If the group determines that the child's behavior was a manifestation of the child's disability, the IEP team shall -
(i) conduct a functional behavioral assessment, and implement a behavior intervention plan ...
(ii) in the situation where a behavioral intervention plan has been developed, review the behavioral intervention plan ... and modify it, as necessary, to address the behavior; and
(iii) ... return the child to the placement from which the child was removed ..."
(20 U.S.C. 1415(k)(1)(F));
see Wrightslaw: IDEA 2004, page 112)
http://www.wrightslaw.com/heath/disc.behave.why.htm
ROLE OF THE OFFICE FOR CIVIL RIGHTS (OCR)
The Office for Civil Rights (OCR) of the U. S. Department of Education is responsible for enforcing Title VI. "Because it is often difficult for students and their parents to find attorneys to represent them in court cases, the role of OCR is critically important."
"While OCR has authority to initiate investigations without waiting for complaints, OCR has not used this power even to look at the educational justification for the disciplinary practices of school systems with the most egregious racial disparities."
The Project suggests using Title VI to "nudge school systems toward more positive approaches to teaching and discipline that produce better educational outcomes overall."
http://www.wrightslaw.com/advoc/nwltr/2000/nl_00_0706.htm