As the above poster has stated, disclosure is the key. Full, open, non-equivocal disclosure. Don't try to spin it, just be honest. You may need to disclose this on both you law school apps and your bar app, because you do not want there to be a discrepancy between two applications (yes, the bar will compare them).
When you get to law school you will take Professional Responsibility and you will learn that in these matters a cover up or even just a failure to disclose is worse than the actual crime. The bar takes honesty very seriously, and any perceived dishonesty could result in a rejection of your application.
The bar app will probably tell you whether or not you need to disclose juvenile matters. Contact your state bar now, before law school, and get the answers straight from them. They are the only source you should really trust in this matter.
Lastly, at least here in CA, people do get admitted with such problems as long as they are honest and take full responsibility for their actions.