While colleges have the budget to have a professional graphics department oversee the licensed used of their mascot to ensure it's consistency and integrity, high schools do not, and typically rely on generation after generation of student volunteer artists to create art for t-shirts, banners, the yearbook and other school projects. The problem is the lack of consistency. If you had 100 artists draw a panther, they'd all look completely different - each with their own style; and inconsistency is the single biggest factor in deteriorating a brand. The Pillsbury Doughboy doesn't look a lot different now than he did 50 years ago, and for good reason.
Teddy bear clipart is very much in demand today, and not that hard to come by. And if you want it for free, then there are a lot to choose from, but you can't use it for commercial reasons. Many of the sites will allow you to put the images on your own personal website but don't want you charging people to put it on their sites, but don't charge people to use or download it. You won't be breaking any copyright infringement laws as long as you follow the site's rules.