Essential questions help teachers stay focus on big ideas. These questions need to transfer deep understanding to the students and must be answerable as well as to be a sort of "doorway" that leads students to the exploration of core concepts of a certain content.
I understand by this, that in some way students are encouraged to debate, analyze and criticize their understanding of an issue in order to stimulate their deep thinking and relate content, thus, improve their high-cognitive skills. Of course, questions should be shaped around the objective(s) of the unit or they wouldn’t be focused.
I think that these type of inquiries and discussions should be made also by the part of the students, especially teenagers. Why not give them the tools to make "essential questions" on a certain topic by themselves? It's important that students be autonomous critical thinkers because it is something that they will need throughout their lives, not only at school, but also outside of it.
Students need to have the tools to deal with problematic daily issues e.g. drugs, alcohol, morality, etc. only if they have been given appropriate ground and guidance and make them feel their questions are always acceptable.