Nearly 80 percent of Montgomery County high school students who entered their freshmen year in 2005 graduated with a diploma four years later, according to a Virginia Department of Education report released Tuesday.

Of those 756 students, 156 did not graduate by 2009.

The county's on-time graduation rate for this year decreased slightly to 79.4 percent from the 80.4 percent achieved for the class of 2008.

Last year, the state released its first on-time graduation report, which tracks the number of students who earned a high school diploma within four years of entering their freshmen year.

Three of the New River Valley's five school divisions -- Pulaski, Giles and Floyd counties -- had a higher percentage of students meet that mark in 2009 than the previous year, according to the report. Radford's graduation rate also decreased to 84 percent, about 2 percentage points lower than the class of 2008.

Radford Superintendent Chuck Bishop said the drop is partly because of the small number of students in the division.

He praised his staff for knowing why many of those students did not graduate on time. Some became pregnant, others just dropped out.

He said the schools have alternative programs in place, but he admits they can't reach all students all the time.

"We've made great strides, but once that student turns 18 and has the decision to leave school, there's little we can do," he said.

School officials whose divisions improved say the same.

Pulaski County graduated 356 of its 420 students -- improving its graduation rate from 77.4 to 84.8 -- with in June.

Thomas Brewster, assistant superintendent of administration, credited the jump to a credit-recovery program that allows students to retake courses they failed online throughout the school year.

The county has a full-time credit recovery coordinator and also has been part of a state software program that lets schools track student weaknesses, such as English scores or attendance.

"You can't fix what you can't measure, and the fact that we have accurate data and the ability to drill down and look at early indicators helped," Brewster said.

Still, he said the division will continue to work toward getting more students graduated in four years and to monitor whether this year's increase was just a fluctuation from class to class.

"We can't afford to say we're above state average and we're going to stay there," he said.

Statewide, 83.2 percent of the class of 2009 graduated on time.

Brewster touted the school system's "whole child" approach as one way to continue the momentum. That method takes into account factors such as a student's home life and health to find ways to improve their academic progress.

In Floyd County, the graduation rate improved to 88.4 percent from 83.1 percent. Giles County saw its graduation rates improve to 78.5 percent from 77.4 percent.

To see the full report, visit the New River Notebook blog at newrivervalley.com.