It's not hard to find examples of inefficient spending in education (the depiction of Newark Public Schools in "The Prize" is particularly poignant), nor is it hard to find examples of dramatic underfunding (just ask any teacher in a low income area). But anecdotes on either side of the equation don't really lead us to correct policy.
There are costs to operating a school district that have increased dramatically in the past 30 years (most significantly: employee benefits, special education compliance) and have not been met with comparable increases in funding. Additionally, we've dramatically raised the expectations we have for schools (holding schools accountable for "No Child Left Behind" and raising the rigor of instruction with the Common Core & new assessments).
From this vantage point, it seems clear to me that we need to either narrow the scope of what we ask schools to do or increase funding to meet additional burdens. And it'd be nice if we can improve operational efficiency while we do this...