What are the legal requirements for transportation in the I.D.E.A law?

My son was placed at a school other than our home school by the district with a verbal agreement that I could drive with reimbursement. The district now wants him to ride the special ed bus (he has emotional problems). They won't provide the bus or reimburse me what they owe me, which is getting close to $800, unless he (he is 18) signs a legal agreement which contains a non-disclosure statement. Essentially they are blackmailing him into signing it and receiving his free public education. I need help finding the correct parts of the law to protect my son and deal with the district.