Our school is very supportive of robotics. Each year, we do a school wide presentation to show off the robot, and everyone loves that. When we present, our message isn't "I know this is nerdy and weird, but see how cool it can be..." but is "This is super awesome, I love it!" and the enthusiasm spreads.
Since we share a classroom with the video productions class, we get a lot of coverage from them on the school's video bulletin.
Also, we brought two school buses of people from our school and our feeder junior high to the Los Angeles Competition this year, and they all had a blast and it gave them a sense of how big the competition and
FIRST actually is.
Our principle wasn't really supportive until we began doing well, but now he is really into it and came to watch us put the finishing touches on the robot the morning before shipping.