By rubric do you mean the criteria by which it'll be marked and how they'll be weighted? (The meaning I know is the instructions as to what the choice of questions is, but it doesn't make sense not to publish that so that can't be what you mean!) I don't know about in schools, but it's certainly considered good practice in everything I've read about teaching, so it makes sense. The reasoning is that it's just part of clarifying expectations.

Email: my username, followed by 2, at google's mail