ALBUQUERQUE, N.M. (AP) — The grades are in, and top officials with the New Mexico Public Education Department said Tuesday they have concerns about a growing divide among public schools that are earning high marks and those that are failing behind when it comes to student achievement, growth and access to learning opportunities.

The annual report card shows the number of schools across the state earning As and Bs remained unchanged at 38 percent, but 20 more schools earned Fs for the last school year. That included 68 schools that dropped by at least one letter grade to the bottom category.

More than one third of schools in the state's most populous district, Albuquerque Public Schools, earned Fs, marking its highest percentage since the grading system was implemented in 2012. However, the district also saw a slight increase in the number of schools earning As.

Education Secretary Christopher Ruszkowski said in interview that the grades provide a picture of which school districts around the state have made efforts in recent years to adopt reforms aimed at boosting reading proficiency and student performance and those that have taken advantage of mentoring programs for teachers and other school administrators.

"School improvement is a choice. You choose to do the best practices, you choose to buy in, you choose to do the hard work of serving every kid and when you do, look what happens," he said, pointing to the districts that have seen improvements.

The Farmington district, for example, had no schools with grades higher than a B just five years ago. Now, it leads the state with nearly 80 percent of schools earning As and Bs and there were no Fs. The Gadsden and Alamogordo districts in southern New Mexico also have eliminated their F schools.

The Rio Rancho district was near the top with more than 70 percent of schools earning As and Bs.

State officials say the number of students attending A and B schools is up overall from the previous year and 58 schools saw an increase of two or more letter grades. Also, a majority of the state's high schools have been able to improve or at least sustain progress when it comes to college and career readiness and graduation rates, which are factors considered in calculating school grades.

Ruszkowski said the grades show New Mexico students are doing better even as the weight of academic proficiency on the grading system increases.

Teachers unions have criticized the state grading system, saying it doesn't accurately inform parents on whether students are receiving a good education because it is based partly on how well they do on standardized assessments.

Albuquerque district officials say they're not satisfied with the grades assigned to many schools due to the latest assessment scores, but that they have a plan in place to do better. The focus will include early learning, attendance, college and career readiness and parent and community involvement.

In a letter issued Tuesday to students, parents and staff, Albuquerque Superintendent Raquel Reedy said the district is putting more resources back into schools and classrooms and that more than a third of schools and many district departments have new leadership.

As the district rolls up its sleeves, Reedy said it's inviting those in the community to join the effort.

State officials say part of the focus moving forward will be on those two dozen schools around the state that have consistently received bad grades since 2012. A recently approved plan allows for more rigorous intervention by the state in such cases, and parents have the option of transferring their children from persistently failing schools.