The airline is required by law to check that all passengers have the proper documents. When you enter your info online or at the airport the agent must verify the validity of the passport and Visa. After this your boarding pass will say DOCS OK. If the airline fails to do this they can be fined $10,000 and the passenger must be deported on the next flight back if the customs agent cannot verify the information when they arrive at their destination.

While travel agents and airline officials should give the proper information its the passenger who needs to verify the information online as they are the one's traveling. Since they were denied boarding the airline is not legally required to offer any form of compensation and you can be subjected to change fees and be required to pay the difference in the airfare should you want to take the flight again.

I'm sorry if your parent's don't speak or read English well but this is no excuse for being uninformed with the passport laws. They can be translated into different languages.

Its like when you are pulled over by a police you can't say "Officer English is not my first language" and expect any sympathy.

Hope you learn a valuable lesson.