This is a very personal question and I imagine your teacher is looking for your creativity more than a correct answer, but I will provide an opinion that might help get you thinking so that you can write your own idea.
Friar Lawrence's decision to continue hiding Romeo and Juliet's love affair is one that is often debated. As a friar (a religious person) and an older confidant, many have speculated that Friar Lawrence should have helped the young couple come clean and expose their love affair to the families honestly. Taking this idea back as far as it could go, the Friar should not have married the couple in secret in the first place. This is one thing he could have changed that would have prevented the sleeping potion idea later in the story.
Let's assume, however, somehow the marriage still took place, Tybalt and Mercutio's deaths were still the result, and married Romeo was still banished at the moment Juliet is supposed to marry Paris. In this case, again, Friar Lawrence could have simply come clean, or advised Juliet to do so. It seems he was under tremendous pressure from Juliet threatening suicide as well as the apparent anger of Juliet's parents, but you have to wonder if the outcome of telling the truth could have possibly been worse than what did happen as a result of hiding it.