Tinea capitis can not be treated topically, and must be treated systemically with antifungals.
From the en.wikipedia.org
The symptoms of ringworm of the scalp, or tinea capitis, can be severe or mild and most commonly affects school-age children.
From the orlandosentinel.com
Responses ranged from eight percent of directors unnecessarily excluding a child with a cold, to 84 percent of directors unnecessarily excluding a child with tinea capitis.