A great inexpensive and fun date for teens is to have a baking night. The couple will need access to a kitchen (and hopefully nosy parents will stay out) and ingredients to make some yummy food.
Baked goods are less pressure than cooking a full dinner, so perhaps start by whipping up some cookies or brownies - even if they are made from a store bought mix.
The time together in the kitchen allows the couple to talk and get to know each other. They also learn how to work together as a team while baking and see if they are truly compatible.
Baking also provides the opportunity to be flirty and fun without the stress of being in a public place like at the movies or at a restaurant.
Also, everyone loves to eat so why not make something delicious together?