Four-year graduation rates were on the rise at a majority of Montgomery County high schools from 2010 t0 2012, according to state figures released last week.

Of Montgomery’s 25 high schools, 16 saw an improvement in graduation rates during the two-year period, and nine showed a dip in the proportion of students earning diplomas on time.

Overall, Maryland’s rate rose 1.5 percentage points over two years, to 83.6 percent for the class of 2012. In Virginia, officials recently announced, the rate was 89 percent, about the same as a year earlier.

Montgomery County’s results showed an increase of 1.3 percentage points from 2010 to 2012, for a four-year graduation rate of 87.4 percent across the district of more than 151,000 students.

The greatest uptick in Montgomery, from 2010 to 2012, came at six high schools, with Watkins Mill High School in Gaithersburg improving the most — 6.5 percentage points, to 85.3 percent, from 78.8 percent.

Other schools that fared well in the new numbers included Northwood High School, climbing to 81.6 percent, from 76.4; and Walter Johnson, rising to 96.7 percent, from 91.9 percent.

In addition, Rockville increased to 85.7 percent, from 82 percent; Montgomery Blair edged up to 85.4 percent, from 82.6 percent; and Thomas S. Wootton improved to 98.7 percent, from 95.9 percent.

Of the nine high schools that lost ground, five showed rates down by one percentage point or less over the two-year period. The greatest decline came at Springbrook High School in Silver Spring, where the rate dropped 1.9 percentage points, to 81.5 percent, from 83.4 percent.