normal walking is about 5 mph
that's 5 miles in one hour or 1 mile in 1/5 of an hour = 60/5 = 12 minutes
6 mph would mean a 10 minute mile
6.5 mph would mean 60/6.5 = a 9.23 minute mile, which is really just a fast walk.
Most students could walk a little faster than a normal walk. They're young and physically healthy enough.
It might be more accurate to say most students have
mile times less than 9.375 minutes. Most could walk 6 1/2 mph and most could run faster than 6 1/2 mph.