* By student enrollment: This fluctuates yearly and reliable, up-to-the-minute data isn't consistently collected and published nationally. Different schools might claim the title depending on the year and how enrollment is counted.
* By physical size (square footage): Again, this information isn't centrally tracked. A massive, sprawling campus might not necessarily have the highest enrollment.
Therefore, there's no official, universally agreed-upon "biggest" high school in the US. Any answer claiming a specific school would be based on limited, potentially outdated information.