Dear Pedro,
At that age, your students should be searching for direction and motivational forces towards upcoming life goals. Learn more about them and utilize what information you find out to motivate them to learn language. As soon as they realize that a language is just a medium of communication, solict reasons why speaking a foreign language would benefit them in the future. Keep on asking them right up till exhaustion... then ask them if they can think of just one reason why learning another language would be detrimental to their future.
If your students are all Catholic and in high school, you could always role play that one student in your class will have the opportunity to study abroad in a native English-speaking country. While there, he or she will become friends with an English-speaking student who is also Catholic. Would your student know the Lord's Prayer in English?
Our Father, who art in heaven,
hallowed be thy name.
Thy Kingdom come,
thy will be done,
on earth as it is in heaven.
Give us this day our daily bread.
And forgive us our trespasses,
as we forgive those who trespass against us.
And lead us not into temptation,
but deliver us from evil.
For thine is the kingdom, the power and the glory forever and ever. Amen.
How is this to motivate your students to ask a question?
Sincerely,
Eric Paul Monroe
http://www.eric-tesol.com/