Keep close to a normal school timetable.
With the removal of things like travel times, the school day is much shorter than it was pre-lockdown, so there is not as pressing a need to get up so early. However it is still crucial to keep to a regular timetable, and maybe even try things like wearing your school uniform. This helps keep you in a school mindset, and allows you to fully apply yourself to your work. Resisting the temptation to sleep till midday everyday may be difficult, but it's definitely worth it and does wonders for your ability to apply yourself fully at home. Make sure also to schedule in breaks, as after too long sitting staring at a screen it becomes much harder to concentrate.