That's so interesting! My county is super small but my school is on the border of two different counties, so there's a major road close to our school. I can't think of any major accidents in the past six years connected to my school and our open lunch.
All the HS's in my county have some sort of Senior requirement to graduate. My school has Senior Project and it's a class period built into the school day, you're allowed to leave during this period in the second quarter. Most use the time to complete some service or internship requirement but you can also just use it to go home early or come to school late, or get a late lunch as the period is 1.5 hours long. The other school in our county has 'senior experience' where Seniors use the last month of school to intern/work. About three years ago, a kid died during this period because his friends were driving a car and pulling him along on a skateboard. They debated changing the protocol because the students weren't using the time the way they were supposed to but I don't think they did. At least with our version of Senior Project students still are required to be in school for most of the day.