Timing of Letters to Peer Schools re: Scholarship Offers Forum

[crombot]

Okay, so I am under consideration for scholarship at a School X that I would really like to attend, but have a great scholarship offer from a peer institution, School Y. Should I send School X a copy of the offer from School Y ahead of time, or wait until I receive the initial offer from School X (if any)? I don't want to seem presumptuous, but at the the same time, I won't attend School X if they don't at least match School Y.

(You can probably easily figure out which schools I'm referring to, but I'd just rather not name them on this post.)