Headlights stay on in 91 festiva ! with switch

The headlight switch is on the left lever that comes out of the switch box that is under the steering wheel. You would need to remove the connector that is under the cover that covers the steering column. You can pull the connector apart coming from the switch box under the steering wheel and test for continuity on the switch terminals when you move the switch from on to off. You will need a wiring diagram or some careful tracing of the colored wires to determine which connectors to test.

The headlight switch is most likely defective. If you can get to the back of the switch you can do a continuity test to see if the switch is opening and closing.