Having taught students from the ground up many, many times, we've already covered a huge amount of ground even before we get to Modes. I feel there are necessary steps in progressive learning that should be covered and understood before a beginner dives in to something like Modes. (and no, that's not because learning the Modes is hard, by the way!)
More often or not, if a student comes to me to tell me about Modes their misunderstanding has come about because of the lack of theory preparation. The very building blocks, as it were.
An elementary example would be "I'm playing Aeolian, because this is the Aeolian pattern on the bass."