It's wrong to lie to your parents.
Lucas got a disciplinary note from his teacher to give to his parents.
Lucas wants to go to his friend's slumber party that night.
Lucas gives his parents the note and explains to them how he has learned from the situation.
Lucas tells his parents he had a good day at school and goes to the party.
Lucas's parents can see that Lucas is making an attempt to be better and allow him to go to the party.
Lucas's teacher calls his parents the following week about the note and Lucas gets grounded for having lied to them.