An Ann Arbor middle school teacher went to work in the 2010-11 year with a starting salary of $38,670. In 2017-18, her final year with the district before moving to a career tech center, her salary had risen to $56,192.

This teacher’s annual pay increases averaged 5.4% during those years. Had her pay continued to increase at that rate, she would have been getting an annual salary of $112,483 by her 20th year.

But that’s not how it works in Michigan’s unionized public school districts, where labor contracts put new teachers on a salary fast track for their first 10 years or so. After that, the same union-negotiated contracts then cap what the most experienced teachers can earn, leaving them with largely stagnant salaries for the balance of their careers.

This is not a secret and not a surprise to teachers who reach that top point on the union pay scale. It’s part of the deal they accept when entering the career: Your pay will increase rapidly at first and then not at all once you’re a veteran. But the deal also includes job security, health insurance and retirement benefits that are rare in American workplaces.

In Ann Arbor, the union contract mostly ends pay hikes after 10 years, except for a bump in the pay of teachers with 12 years of experience. Teachers may also enjoy an occasional across-the-board increase that boosts the entire pay scale by a modest percentage.

Neither amounts to a large salary increase.

Ann Arbor teachers with 10 or more years of experience would have seen their top-of-scale salary increase by just $1,678 from 2009-10 through 2018-19.

In 2009-10, the contract negotiated by the teachers union local, the Ann Arbor Education Association, prescribed a top-of-scale salary of $79,899 for someone with a master’s degree. By 2018-19, a teacher with those same credentials would top out at $81,577. The average Ann Arbor teacher’s salary in 2017-18 was $71,546. Statewide, the average teacher salary that year was $61,908.

The vast majority of Michigan teacher contracts severely limit what the most experienced instructors can earn. And about half of Michigan’s public school teachers have 10 or more years of experience. (According to the most recent state data, in 2016, 51% had 11 years of experience or more.)

Some teachers are in school districts like the Troy School District, which has a robust pay schedule with a top salary of $96,200. In less affluent districts, such as Eau Claire Public Schools in Berrien County, a teacher reaches the top of the pay scale at $62,224 after 17 years.

Cara Lougheed is the 2019-20 Michigan teacher of the year. She teaches English and history at Rochester Community Schools and has 21 years of experience.

Lougheed’s total salary was $92,748 in 2013-14. In 2017-18, however, her total pay was less, $89,424. Like many teachers, Lougheed earns varying amounts of extra pay from year to year for accepting extra duties. Taking on fewer extra duties means less in extra pay.

Rochester’s union-negotiated pay scale caps teachers’ salaries when they have 20 years on the job. After that, these teachers get an annual bonus of up to $550.

Lougheed’s situation is typical of Michigan teachers who have reached the top of the union pay scale. If they don’t take on optional extra duties, and in the absence of occasional across-the-board increases, their pay remain stagnant for the balance of their careers.

The system can produce some unusual pay-hike dynamics within a single district. For example, a first-year teacher at the Troy school district who began in 2014-15 with a $36,071 salary was making $55,237 by 2017-18, an increase of $19,166 in just three years.

By comparison, a Troy teacher with 20-plus years of experience made $92,413 in 2007-08. Ten years later in 2017-18, her gross salary was $95,530, reflecting far more modest increases.

The current Troy Education Association union contract caps annual raises after 14 years. Teachers get longevity bonuses of up to $7,700 every five years, starting with the 15th year.