The amount of sleep your teen is getting and the regularity of their sleep schedule is most important, so sleeping until the late morning may actually be okay.
Bedtime Routine to Help Kids 6-8 Transition to the School Day
Why is my teenager sleeping so much?
Sleep for kids & pre-teens: 5-11 years
The Evidence on Kids, Sleep, and School Start Times
My Son Sleeps All Day and Is up All Night” - Parents Ask
My teen is sleeping all day, should I be concerned? - Children's National
A tired child? What you should know - Harvard Health
Sleep and teenagers: 12-18 years
8 No-War Ways to Get Your Teen Out of Bed for School - Raising Teens Today
My teen is sleeping all day, should I be concerned? - Children's National
When Should Kids Stop Taking Regular Naps?