In most U.S. states, a 15-year-old cannot legally drop out of high school without parental consent and often with the approval of school officials. Even with consent, there are usually restrictions and requirements that must be met. The specific rules vary significantly by state. Some states might allow it under certain circumstances, such as demonstrating an ability to pursue a GED or vocational training. However, it's generally much more difficult for a 15-year-old to drop out than an older student.
In short, while technically possible in some limited situations, it's highly unlikely and requires navigating complex legal and educational hurdles.