The main driver is increased state spending on health care, particularly Medicaid. That spending, which is mandatory, crowds out education funding, because states have a balanced budget requirement. Medicaid spending in Illinois, for example, is up 141% since 2000 and health care is 25% of the state budget. Obamacare, which did nothing to control health care costs, actually expanded Medicaid eligibility.

https://www.illinoispolicy.org/health-care-costs-consume-25-...