My D got into a flagship state school when she was 16, graduated at 19, and now a PhD student. She didn’t take GED. I’m not sure about now, but at the time, in CA, a person has to be at least 18 yrs old to take GED.
Her stats were excellent, however: 2360 SAT (old score, 1 sitting), 4 SAT subjects (lowest score: 790), 7 AP exams (all 5). She also had 27 units of college-level classes (higher than AP, evaluated by the university she matriculated at) from the work she did at Stanford EPGY.
So yes, it is possible, even without GED.