Standardized test scores due out later this week are expected to show that the state takeover of the Lawrence school system is having a positive impact, according to three people briefed on the results.

The three people all said a turnaround was taking place in the Lawrence schools but declined to comment on the record or provide any specifics about the MCAS test score results, which are due to be released publicly later this week. Jeff Riley, the state receiver of the Lawrence schools, declined comment.

State education officials placed the Lawrence school district in receivership in the fall of 2011 because of chronic low student achievement, the first time that power had been exercised under a state law passed in 2010. At the time, Lawrence was in the bottom 1 percent of all school districts in the state, with just 30 percent of students scoring proficient or above in math and only 41 percent proficient in English. Half of the system’s students were dropping out. Nearly 90 percent of the district’s students come from low-income homes.

Riley, who was a deputy superintendent in the Boston public schools, took over in Lawrence during the summer of 2012. Instead of imposing a new education approach for the district from the top down, he decentralized power, giving principals and teachers the authority to devise turnaround plans tailored to their individual schools. He also extended the school day and brought in successful charter school operators to run two of the city’s schools, open a high school targeting dropouts, and launch a math tutoring program.

As the state overseer, Riley has been allowed to manage the schools without interference from the elected Lawrence School Committee and the teachers’ union. Riley has used his ultimate power sparingly. He fired only two of the 900 teachers in Lawrence, while another 31 retired or resigned during the initial state takeover process and another 15 were put on improvement plans.

Still, Riley and state officials have come under intense fire from the Lawrence Teachers Union, which has accused state education commissioner Mitchell Chester of trying to undermine the union with the turnaround plan Riley has put in place. In April, the union filed two complaints with the state Labor Relations Board accusing Riley of failing to negotiate a new contract. Others said at the time of the state takeover that the Lawrence turnaround plan didn’t go far enough, suggesting that a wholesale replacement of district schools with charter schools was called for.