NFHS Clock question

So I've been tabbed to run the clock/scoreboard for my son's V HS games. But I have a question on restarts.

I know to look for clock stoppages:
* After a goal
* Before issuing a caution
* After an injury (depending on how long it takes to work out)
* Sub by the winning team w/less than 5 minutes in the half

So my question is, when should the clock start? On the whistle? When the ball is actually in play (when it's kicked or thrown)?

I know we're only talking maybe a 30 second...

NFHS Clock question