"Blessed are they who hunger and thirst for righteousness, for they shall be filled."
[MEANING] It means that the ones who are after what is right will get what they want.
[EXAMPLE] Even with something as simple as quizzes can help you show this. When the teacher has incorrectly checked an item in your quiz, tell him/her that it is incorrectly checked.
"Blessed are the merciful, for they shall obtain mercy."
[MEANING] It means that the ones who have mercy on the less fortunate will get mercy from them.
[EXAMPLE] Simply giving a beggar his/her basic needs will be an example of this beatitude. You never know, he/she might be able to help you in the future...
"Blessed are the peacemakers, for they shall be called children of God."
[MEANING] It means that if you bring peace into the world, God will call you His son.
[EXAMPLE] The sacrament of priesthood - the sacrament where ordinary people become "married" to The Lord while preaching His Word. Think - if you were a priest, wouldn't you be sharing peace to the world through God's Word?