LOL don't know about school sponsorship but I definitely fished as a school activity back in the day.
This was 1984. My friend and I arranged our school schedule so that we had all of our senior classes in by 10:00 AM, after that study halls and lunch and report to the Vo-Tech at 1:00 PM for computer stuff rest of the day. At 10:00 AM we'd sneak out to the car and fish until 12:30 and sometimes longer if we could get somebody to sign in for us at Vo Tech. My mom used to wonder why my friend showed up in the morning with his canoe on top of his car

Back then you could get away with a lot more, study halls were unsupervised (quite often) et all.
What would be sweet is if the school picked up the cost of equipment. We used to spend every last dime we had on lures. Imagine the collection you could amass with the school picking up the tab?