And I agree with PP when he says "It depends."
![Grin :D](./images/smilies/biggrin.gif)
There's another thread ( "XC ruin pole vault?" ) http://polevaultpower.com/forum/viewtopic.php?f=30&t=15420 that offers additional advice about XC for pole vaulters.
This is a controversial topic and there's no single right answer.
Although PV is a very specialized sport (event), it requires similar overall fitness and coordination to what other sports provide - including XC.
Generally, good high-school pole vaulters are (or need to be) good all-around athletes, with a willingness to train hard and an interest in multiple sports or track events. This includes sports and events that excercise your legs (sprints, XC, LJ, HJ, TJ, soccer, basketball, and almost any other sport), and upper body strength & coordination (gymnastics is perfect).
I never specialized in PV until I went to university. I loved playing HS basketball so much that I would never ever give that up, just to be a better vaulter. To be honest, if I had a choice between a BB scholarship and a PV scholarship, I would have picked BB. I just wasn't that good of a player, but I loved "teamwork".
That doesn't mean I didn't also love PV. I loved both sports. I just had to compromise - to find the right balance between the sports that I was interested in, and the sports that I did well in.
So my advice is that you should try lots of different sports (and events) in HS - including XC (if that's what interests you, or if you think it's a good off-season sport and you can stand the monotony of "just running").
As SinCity said, that's how you find out what your best sport (or event) is. And if these other sports help your conditioning during the off-season (which I think they do), then all the better!
Kirk