Teen morning slowness is one of the most well-documented phenomena in adolescent biology. The circadian phase delay of adolescence is real, consistent, and independent of screen use or habits, though those can compound it. Asking a teen to be fully functional at 6am is, for many, neurologically similar to asking an adult to be fully functional at 3am. The American Academy of Pediatrics has recommended school start times of 8:30am or later for exactly this reason.
I am not going to fight your biology. Let's figure out the minimum viable morning together.