On Monday, The Washington Examiner's Rachel Baye reported that the D.C. Public School system is negotiating with the Washington Teachers' Union to implement longer school days and a longer school year. WTU President Nathan Saunders expressed openness to the idea but said such a change will come at a price to the school system -- higher pay for educators and more hours for "professional development." Meanwhile, Baye noted, some D.C. public charter schools, which have greater flexibility and freedom from union interference, have already gone ahead with longer days and longer hours.

It is good to see DCPS try something new, and to innovate based on the proven success of charter schools such as those run by KIPP DC. Basic student proficiency within the DCPS system remains abysmal, and charters continue to outperform them despite being shortchanged on facilities funding.

But negotiations over the length of the school day also underscore the DCPS system's lack of flexibility, which is one factor in its persistent failure, and in its current decline in student enrollment as parents choose charters instead.

Saunders must be careful offering concessions on the length of the school day. Former Chicago Teachers Union President Deborah Lynch was ousted from her job last decade by CTU members. Lynch's offense was that she agreed to add just 15 minutes to Chicago's then-shortest-in-America school day in exchange for a seven-day reduction in the school year and large pay increases for her members.

The Chicago example, and the relative success of D.C. charter schools compared to the DCPS schools they compete against (the ones outside Wards 2 and 3) both serve as examples of how ill-suited the classic unionized model is in a field like education. Strict work rules and strict seniority pay, all defined in adversarial contract negotiations between management and labor, might have worked well for the assembly-line workers in Detroit who for decades epitomized the union ideal.

But teachers are not assembly-line workers, nor are children widgets. Teachers deserve to be paid well, but their commitment to the children they serve depends largely on their willingness to be flexible. And the choice that parents are making now -- as they put an ever-increasing percentage of the city's public schoolchildren into charter schools -- is a reflection of these realities.