people forget how many bad teams there are
If were talking average based on team/school, 55-56 seconds to make the relay team.
This is because there are many more small schools than large schools, even though a majority of students probably attend large schools based on population distribution. There are lots of small schools out there that only have a handful guys who can break 1 minute. The 4x4 D team from a large school outside of Philadelphia will probably beat the 4x4 A team from somewhere in Vermont.
If the population was evenly distributed that number would be closer to 53.
I remember a couple times in HS when we'd go against some of the not-so-good teams in the county, the coaches would throw me on 4x4 running 57-58 (I'm a distance runner and I was tired from the mile, 800, 2 mile etc.) and we'd win the relay in like 3:50.