The "school years" aren't what you think
Under federal law, eligible students receive special education through age 21 — age 22 in some states. The school day ends at 3 p.m. It doesn't cover summers, holidays, or sick days. Traditional after-school programs will not accept a child who needs total care.
For working parents, this is a daily logistical impossibility: be at work, and be the only person qualified to care for your child every hour the school isn't open.