The true long-term impact of the Chicago teachers strike may be not be known for some time. But there is no mystery about its impact in the immediate term -- anxiety, panic, and disruption for myriad mothers and fathers left in the lurch when 30,000 members of the Chicago Teachers Union walked away from their classrooms last week just as a new school year was getting underway.

"Parents and guardians frantically sought last-minute child care, pleaded with their bosses for leniency, and hoped that their kids would return to school sooner rather than later," reported the Chicago Sun-Times . "Citywide, for thousands of families, stress was high." The paper quoted Martina Watts, a mother in West Garfield Park, one of the city's rougher neighborhoods: "I might be losing my job over this. As long as they're on strike, I can't work. I'm not getting paid."

Construction worker Allen Packer told a TV interviewer that he had to switch from full-time work to a part-time night shift so he could be home with his young daughter during the day. "I kind of understand what they're trying to do," he said of the striking teachers. "But this is not just them." He gestured toward his daughter. "It's her education, first of all. Then my paycheck for the food."

The union went on strike to block school reforms proposed by Mayor Rahm Emanuel, especially a tough teacher evaluation system based on student test scores. The chaos and financial hardship inflicted on so many Chicagoans -- more than one-fifth of whom have incomes below the poverty rate -- was not an unintended consequence of their walkout. To the contrary: The sudden dislocation, the harried scramble to find emergency day care, the extra expense, the turmoil in the children's routine -- they were at the heart of the union's strategy. The Chicago Teachers Union knew that by going on strike it would put countless families in an impossible position. That's what it was counting on.

When public-sector employees refuse to work, innocent bystanders are always the victims. Unions are well aware that by walking off the job, their members can deprive a huge swath of the public of what are frequently essential services -- trash collection, public transit, air-traffic control, classroom teaching. Since those services tend to be legally sheltered monopolies, a union strike leaves the public with few alternatives. Shut down the schools or let the garbage pile up, and voters grow desperate or angry. As public impatience mounts, elected leaders will usually decide they have no choice but to give the union what it wants. Rare is the official who can resist that kind of political pressure.

The private economy is different. Striking workers at a private corporation may demonize management as heartless plutocrats and greedy "1 percenters" who deny employees the pay and perks they deserve. But while union rhetoric can be ridiculously exaggerated, labor disputes in the private sector generally boil down to an argument about economic equity: Workers deserve more of the profits they helped generate. If those workers walk off the job, both sides pay a price -- the company loses business, and employees lose income. Seldom does public opinion play the deciding role. That's because a strike against General Motors or Shaw's Supermarkets doesn't leave consumers with nowhere else to go.

By contrast, when public-sector unions call (or threaten) a strike, their strategy isn't to starve management of revenue. It is to cause maximum distress to blameless third parties – ordinary residents – and then deploy that distress as a weapon. That's not economic equity. It's raw power politics.

It's also egregious. In Chicago, the average public school teacher makes more than $76,000, according to union figures -- half again as much as the average private-sector employee earns. Over the past nine years, Crain's Chicago Business reports , teacher salaries in Chicago have climbed 42 percent. And what have Chicago taxpayers gotten in exchange? One of the worst public school systems in America, with a graduation rate of only 55 percent . "Of 100 Chicago Public School Freshmen, Six Will Get A College Degree," a headline in the Chicago Tribune announced in 2006.

Only in government work would employees claim that so lousy a record entitles them to still more hefty raises, or to a level of job security virtually unheard-of in the private economy. Such an outrageous sense of entitlement is among the poisoned fruit of public-sector collective bargaining , which empowers union officials with influence they have no right to -- influence they preserve by exploiting other people's pain.

: Undergraduate tuition at George Washington University in 1975 was $2,500, not $2,400 as I wrote in Wednesday's column