The student will have to explain absence from school, and homebound status, and possibly the dip in grades w/out accommodations. The guidance counselor may have to as well. Perhaps there is a possible cover story, particularly since most kids were at home during COVID restrictions and many had dips in grades. But if someone had cancer they would disclose, and major depressive disorder is also an illness.
We all post based on the experience of our families and others we know, but there is a basic legal principal involved here as well.