articleThe Brief Burger King is working to lure in customers this back-to-school season with a free King Jr. The free King Jr. Burger King is sweetening the return to school for kids by offering a free King Jr. The fast food chain said customers who spend at least $10 between Aug. 12 and Aug. 25 can get the free King Jr. Burger King is among the various food chains that has been dealing with price-conscious consumers by offering value meals and deals.