IDEA funds are disbursed through grants to the states, which then use some of them for state-level disability-related services, and flows the rest though to LEAs (local education agencies). I would be really surprised if only one percent of disability-related spending in your district was funded through IDEA. Your district might be counting the state-distributed IDEA grant money as coming from the state, or the document you were referencing might be looking at Federal dollars as a percentage of the overall district budget, in which case I would not be surprised to see a fairly low percentage funded through IDEA, since the majority of students aren't disabled, and the majority of students with disabilities don't need special education and related services (IDEA), just accommodations and modifications (504), which generally cost the school system nothing. The regular education budget really dwarfs the special education budget in most districts.
