AMONG MAJOR suburban school systems in the Washington area, Montgomery County stands out for paying its teachers the highest salaries, by far, and providing superb benefits. Now, faced with a choice between plumping up teacher pay even more or devoting more resources to the classroom — cutting class sizes, say, or restoring staff — Superintendent Joshua P. Starr has decided on the former.

By crowding out other initiatives and hiring, that ill-advised decision may undercut the quality of education in Montgomery. Unfortunately, it is typical of a school system that has long been pliant to a powerful teachers union.

The proposal by Mr. Starr is out of line with other top-notch school systems. It would give most of the county’s 12,000 teachers not one but two raises — the first in July, the other next May — with the distinct possibility of a third increase (sure to be demanded by the union) later next year. Together, the first two raises would boost the average teacher’s salary to around $80,000, up from $74,700 today.

It’s not a question of whether teachers deserve a raise; they do. Along with their counterparts in other excellent school systems, most Montgomery teachers are dedicated, hardworking and effective. Their pay has been frozen for the past two years.

But a two-step increase averaging nearly 7 percent for about three-quarters of the county’s teachers is neither good policy nor affordable.

Over the past couple of years, the schools decided to maintain unusually generous health benefits for teachers and other employees, and to refuse pay cuts, in the form of furloughs, that befell other county workers. But there was a trade-off: Class sizes were increased, and the schools laid off scores of preschool, music and reading teachers, as well as career counselors, special education instructors and teachers focused on helping struggling pupils.

Teachers themselves have complained that the cuts have short-changed students. “There are actually fewer teachers and instructional assistants there to help,” said Joshua Rubin, a special education teacher at Einstein High School. He is one of several teachers who speak movingly about the impact of layoffs in a video prepared by the teachers union.

But when the union is at the negotiating table, it puts the salary demands of teachers ahead of the interests of children. For just half the cost of the scheduled $65 million in pay raises, the schools could have cut average class sizes by two students or restored scores of classroom positions eliminated in the last few years.

The planned raises will outstrip those of other county workers (who are getting bonuses rather than base pay increases) as well as those set for teachers elsewhere.

In Fairfax, for instance, the net pay increase for most teachers in the coming year will be less than 2 percent, with no commitment for next year. (Like Montgomery, Fairfax froze salaries for all school employees for two years during the recession.) On average, Montgomery’s scheduled increases will leave salaries for its teachers about 20 percent higher than their counterparts in Fairfax.

Higher base salaries will drive up pension costs, which will be passed on to taxpayers indefinitely. They will complicate contract negotiations with other county workers, including police and firefighters, who will demand commensurate raises.

The more serious concern is that Mr. Starr is boxing himself, and the schools, into a corner. By increasing pay so abruptly, he will have no option but to ask the County Council for much higher budgets in the future if he wants to address systemic problems.

Unfortunately, the county’s recent experience with exceeding state-mandated school spending levels has been painful, and council members are unlikely to repeat it. Doing so locks the county forever into a higher base of per-pupil spending, from which retreat is almost impossible — even if revenues plummet. Whether or not it’s desirable to push school spending beyond the state-mandated minimum, it’s fiscally irresponsible.

Mr. Starr, in his first year on the job, appears to have calculated that it is safer to appease the union than to pursue classroom improvements. He insists the schools must show they value employees in order to maintain morale and retain good teachers.

But comparable school systems have been able to convey that message with more affordable pay increases. Mr. Starr’s approach may buy him a short-term honeymoon with the union. In the long term, it’s unsustainable.