Maryland Gov. Larry Hogan. (Patrick Semansky/AP)

Gov. Larry Hogan (R) said Thursday that he plans to propose legislation during the 2018 legislative session to eliminate state taxes on all retirement income for military veterans.

"Not only is this a deserved benefit for those who have served our country, this bill will also make Maryland more competitive with other states in our region that already offer this benefit," Hogan said in a news conference the day before the federal holiday for Veterans Day.

The proposal would be an expansion of a current tax credit for veterans. Two years ago, the General Assembly passed legislation that increased the tax exemption on military pensions from $5,000 to $10,000.

Hogan proposed exempting all military retirement income from state taxes in 2015 and 2016, but the General Assembly did not approve those bills.

In 2018, the governor said he plans to "push the heck out to get it done."

Hogan declined to say how much the tax cut he was proposing would cost. Legislative aides say previous proposals were projected to cost $100 million over four fiscal years.

At the news conference, Hogan said he was "outraged" over what he called "disturbing" results in a recent audit of graduation rates in Prince George's County.

An investigation found that nearly 5,500 students in the school district during the past two years had their grades changed in the days before graduation.

The 211-page report pointed to problems in grading and student absenteeism but did not find that tampering was ordered by the school district's leadership, including schools chief executive Kevin Maxwell.

Maxwell has called the probe "political" but also said the school system would take "appropriate disciplinary action" as needed and problems would be "corrected with a sense of urgency."

Hogan said the county's response so far doesn't seem urgent enough.

"I was frankly not only outraged at the report findings but I was somewhat outraged at the response again by Prince George's County that doesn't seem to want to take it seriously," Hogan said, answering a reporter's question. "They better start taking it much more serious."