It's 100% certain it's a concussion. Being there to see the violent hit, the aftermath with the classic head trauma sign of holding ones face mask to stabilize oneself, seeing him right in front of me on the field walking off woozy looking, and from the in game notification sent out from the school re the hit makes this one an easy conclusion (again just like the two last year, which hopefully this year I won't have to engage with the less informed here re the reality of it).
This because you don't need head trauma to get one with the violence of the hit re whiplash enough to cause it. The fact that he was back on the sideline is good and means it wasn't a grade 3 concussion (which is usually the case with indirect concussions from whiplash without a direct hit to the skull). Grade one for sure and possibly grade 2 which will only be known by follow up neurological testing this week.
Regardless this is number 3, it would be crazy to put him out there next week regardless and the protocol would suggest against it (especially if it's grade 2):
Concussion Rating Scale
If I'm his parents I shut him down for the season given his history. Possibly his career. Its wasn't a stinger as, again, was right on the sideline and no upper extremity symptoms were present nor addressed.
(This is going to be my one and only one post on this this year as I'd prefer not to have to go through what was gone through last year with the dopey back and forth only to have it ultimately substantiated).