Montgomery County officials on Wednesday butted heads with school officials over school employee raises, which the county says is excessive and could ultimately undermine student learning.

School officials announced on Monday that their workers would receive the first raise in three years. The raises — which cost about $25 million, according to the officials — are part of a $4.6 billion operating budget that the Montgomery County Council is expected to approve on Thursday.

The size of the raise depends on a number of factors, including current salary and length of employment. The increase, which will be permanently added to the employees’ salaries, is about 5 percent on average, according to county and school officials.

County officials, on the other hand, approved a $2,000 one-time lump-sum bonus for their employees. They said they should not spend more until the county’s economic situation improves.

Though county unions agreed to the one-time bonus, they still weren’t happy about it. In a letter to the Montgomery County Council this month, Gino Renne, one of the county union presidents, decried the “ever-widening gap” in compensation between school employees and other government workers.

Before Monday, school officials indicated that they would approve a raise of only about 3.4 percent. Still, county officials urged them to grant only the $2,000 bonus.

The school officials declined. In fact, they added to the raise.

In a letter to county officials on Wednesday, Superintendent Joshua P. Starr said the school system is still practicing fiscal restraint by finding more than $9 million in budget cuts to help pay for the wage increases.

“Ultimately, a dollar-for-dollar comparison of our employee salaries and benefits is not relevant given that the work and demands of our employee groups are very different,” Starr added. He said the school employees have struggled to maintain the school system, which he described as the county’s “signature element.”

County officials received the letter Wednesday afternoon. They fired back within hours.

County Executive Isiah Leggett (D) and County Council President Roger Berliner (D-Potomac-Bethesda) wrote that the increase “raises serious questions” about the school system’s future ability to address “critical classroom needs,” such as reducing class size and improving student learning.

In response, Dana Tofig, a spokesman for the school system, referred comment back to Starr’s letter, saying it “speaks for itself.”