For Kevin Pace, the president’s health-care law could have meant better health insurance. Instead, it produced a pay cut. Like many of his colleagues, the adjunct music professor at Northern Virginia Community College had managed to assemble a hefty course load despite his official status as a part-time employee. But his employer, the state, slashed his hours this spring to avoid a Jan. 1 requirement that all full-time workers for large employers be offered health insurance. The law defines “full time” as 30 hours a week or more. “We work so hard for so little pay,” he said. “You would...