BEL AIR, Md. – The teachers of Harford County are planning to “work to rule” this fall, because they’re not happy about recent layoffs and a school board decision to cancel their scheduled raises.

This is a tired old tactic used around the nation by union teachers to make students suffer over adult financial disagreements.

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It means teachers will agree to do only duties specifically stated in their collective bargaining agreement, but no extras like helping students before or after school, chaperoning field trips, or sending letters of recommendations to colleges on behalf of seniors.

Such a strategy demonstrates the low regard the union has for students. But that’s hardly a surprise. Just about every time a teachers union gets angry about something in America, kids suffer.

The union’s action was prompted by a decision by the county school board to lay off staff, cancel a pending raise for staff members, impose pay-to-play fees for student activities and consolidate bus routes this year, according to the Baltimore Sun. Those decisions were necessary because the county board failed to provide $20 million worth of extra funding that the school board requested for the coming school year.

Ironically, the school board requested the extra $20 million to keep up with union-inspired pension and salary costs, according to the news report. The county board noted that school funding has already increased 26 percent since 2006 while enrollment has declined by 2,500 students in that time.

So the teachers are going to make student suffer because one group of politicians wouldn’t give another group of politicians as much money as it requested.

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Enough of this nonsense.

The people of the Harford County school district should answer this cynical challenge by volunteering to perform as many of the extra tasks that the teachers are abandoning as possible.

They should chaperone the dances and field trips, decorate the school, set up tutoring services for students, and fill any other gaps they possibly can. And they should continue to perform those services indefinitely, perhaps even permanently.

Then the school board will be able to tell the union that the extracurricular services of its members are no longer necessary or wanted. The teachers can “work to rule” until the cows come home and nobody cares.

But they should also tell them that their stubborn resistance to a little extra work will be remembered when contract time rolls around and the teachers want another across-the-board raise. That’s when the board should tell them “Sorry, but we only provide raises to full-service teachers who dedicate themselves to their jobs, regardless of political conditions.”

If the union wants to make its members less valuable to the school district, so be it. Parents and volunteers (closely screened and supervised, of course) can and should do just about anything the teachers do outside the classroom. Heck, half of them could probably do nearly as well inside the classroom.

This is the only way to effectively deal with the nasty “work to rule” strategy and convince the union that it’s pointless.