If an application asks about expulsions, you must reply honestly, even if you don’t plan to include high school information. In fact, your transfer college may require a high school transcript, although you are applying as a GED recipient. (Note, however, that college admission officials put far more emphasis on the college record than on the high school record when evaluating transfer candidates.)
Thus, you need to write a letter to your transfer college(s) explaining the reason for your erstwhile expulsion. Emphasize what you learned from the episode and how you have moved on (providing examples, if appropriate).
Although it’s certainly possible that your past infraction might slip by an admission committee if you decided not to mention it, it’s also possible that college officials could unearth it later on. And if they find that you weren’t fully honest on your application, you could end up with yetanother expulsion on your record!
However, if you want to write back and tell me more about the high school incident, I may be able to advise you more specifically on how to report it to colleges.