Experts agree that many patients show signs of recovery without any therapeutic intervention within 1 - 2 weeks.
Where once it was thought that people under 21 might take longer for this "spontaneous" recovery, more like 4-6 weeks, more recently, experts seem to be finding that even injuries to younger patients often resolve in that same 1 -2 week time period.
I think that it is often best to monitor the person over the first week to see that symptoms are improving.
Those that will experience a recovery without assistance from physical therapy or neuropsychology, for example, should be experiencing less symptoms each day.
If symptoms are not changing or are worsening, this is a clear indication that a concussion specialist should be consulted.
One of the tools that concussion specialists might use is the updated SCAT-6 which is used for sideline assessment and has a pediatric version. This document was updated in the most recent International Sports Concussion Conference in Amsterday in 2023. Check it out, but remember that it is absolutely not a replacement for having a professional assess someone who has had a head injury.