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.
Teens and sleep: Why you need it and how to get enough
Why Is My Child Always Sick? Managing Recurring Illness
Sleep in Middle and High School Students, Healthy Schools
safe kids week Safe Kids Worldwide
Children and Mental Health: Is This Just a Stage? - National Institute of Mental Health (NIMH)
Insomnia: Symptoms, Causes, and Treatment
Is Your Teen Getting Enough Sleep?: Laurel Pediatric & Teen Medical Center: Pediatricians
My teen is sleeping all day, should I be concerned? - Children's National
Ask a Therapist: Why Does My Teenager Sleep So Much?
My teen is sleeping all day, should I be concerned? - Children's National
Moshi Kids: Your New Superpower