Nurses that get drug charges usually face consequences as well...such as losing their license or having restrictions put on it.
It's fabulous that you've completed all the necessary requirements from your conviction and have remained free of substance abuse. However, it is not uncommon for a person to have a "relapse" (not saying that you're one of those people). The licensing board would be remiss in their responsibility if they knew an individual had such a history and didn't at least question the circumstances, outcome, etc.
As far as the school's concerned...they get their money whether or not you obtain a license, they're answer may not been entirely objective.