If I am carrying at a public place and a "school sponsored activity" randomly comes along and enters the same public place where I am already located, I'll take my chances. And honestly, I don't say that often. I almost always error on the side of caution to a fault when it comes to legally carrying. But that line of thinking is absolutely ridiculous on its face.
And you could even take it to the extremes where you are in the Galleria shopping at one end of the mall and a bunch of 3rd graders show up and hit the ice rink and you never even see them. They may not even be in school buses and it may be totally transparent to the naked eye that there is an "activity sponsored by a school" in progress.
So I'm with you. I'm not knowingly going to attend an "activity sponsored by a school" while carrying but I'm not going to dive out a window if a random one shows up where I'm at.
I was jogging down the jogging trails the other day (not on school property) and the entire 7th grade P.E. class jogged past me. Does that mean I was breaking the law? I don't know what classifies as an "event" in the eyes of the law.
ETA:
Yes if your playing putt putt and before finish your game "an activity sponsored by a school" is held you would have to leave or disarm, no were does it require you to be a part of the activity, only on the grounds of or in the building
The law actually states
(a) A person commits an offense if the person intentionally, knowingly, or recklessly possesses or goes with a firearm, illegal knife, club, or prohibited weapon listed in Section 46.05(a):
(1) on the physical premises of a school or educational institution,any grounds or building on which an activity sponsored by a school or educational institution is being conducted, or a passenger transportation vehicle of a school or educational institution, whether the school or educational institution is public or private, unless pursuant to written regulations or written authorization of the institution;
So long as your happenstance encounter with "an activity sponsored by a school or educational institution" was not done either "Intentionally", "knowingly" or "recklessly" you be on good legal footing.