“Not My Department!”
I am a strategic planner. If you tell me what you intend to accomplish, then you need to tell me how you are measuring your progress toward that goal. If your vision and mission statements talk about a goal of student “success”, shouldn’t you measure how many of your graduates acquire post-secondary degrees? A high school degree alone, unless accompanied by skills training for a trade, is not a guarantee of a living wage – clearly a threshold measure of “success”.
In an article in The Chronicle of Higher Education Beckie Supiano analyses a report from the Pew Research Center on “The Rising Cost of Not Going to College”. The economic disparity between younger workers with a college degree and those without is growing. The number of college graduates with career building jobs is also much higher than for those with a high school diploma.
I know that as a superintendent with less than five years in the job, you are measuring the success (or lack thereof) of your predecessor. Nonetheless, if your vision is the success of all of your students, one measure must surely be how many of those students graduate from college. If your graduates are not making a living wage, how can you claim they are successful?
Remember the 1965 Tom Lehrer satire?
Once the rockets go up, who cares where they come down?
That’s not my department, says Wernher Von Braun.
Aren’t we subject to a similar satirical criticism by claiming success is just high school graduation?
The School Solutions Group 
I agree with your thoughts of HS graduation not being the end goal of education. And, we should start from preschool and kindergarten to build learning for life, not for school. Non scholae, sed vitae dicimus!
~Nina