<p>The only time I think dropping a dime would even be REMOTELY admissible would be if you knew about a student whose behavior would be a danger to other students on his/her potential college campus. And even then, you'd have to be 100% sure of your facts and able to back them up. But I'm still not sure it would be any of your/my business to tell any college anything about anyone else. </p>
<p>99% of the time I think the only person whose college admission you should be worrying about is your own (or your kid's).</p>