Graduation rates at Jackson County's public schools plummeted last year, not because fewer students graduated at most schools but due to a new federally mandated formula for calculating the rates, according to a state report released today.

Graduation rates at Jackson County's public schools plummeted last year, not because fewer students graduated at most schools but due to a new federally mandated formula for calculating the rates, according to a state report released today.

The state now calculates graduation rates by counting how many students graduated with a regular high school diploma in four years or less. The old formula looked at the total number of graduates regardless of how long they had been in school compared to the number of dropouts.

The result of the change is reduced graduation rates in all Jackson County school districts as well as across the state, though the number of graduates and how long they took to graduate has remained about the same.

Under the new formula, Ashland High School's rate declined from 93.2 percent in 2007-2008 to 80.3 percent in 2008-2009. Its rate would have been 92.7 percent last year had the old formula remained in place.

Butte Falls logged a rate of 71.4 percent compared to 100 percent the previous year. Under the old formula, last's year rate would have been 79 percent.

Central Point plunged from 97 percent in 2007-2008 to 66.5 percent in 2008-2009. The old system would have calculated its rate at 88.5 percent last year.

Eagle Point's rate also tumbled dramatically from 91.4 percent to 61.8 percent. The drop would have been less drastic under the old formula, 85.6 percent.

Medford, the county's largest district, had a calculated rate of 59.6 percent compared to 78.9 the previous year under the old formula. Its rate would have increased to 83.8 percent last year under the old system.

In neighboring Phoenix-Talent, the rate went down to 65.5 percent, from 71.5 percent in 2007-2008 under the previous formula. Under the old formula, its rate would have been 81.9 percent in 2008-2009.

Prospect's rate went up from 69.2 percent to 84 percent under the new formula, but that's likely because of its tiny population. One student can have a huge impact on the district's rate.

Rogue River had a calculated rate of 60.8 percent last year compared to 92.4 percent the previous year, under the old formula. Its rate would have been 93.2 percent last year had the formula stayed the same.

The statewide graduation rate for 2008-2009 was about 66 percent.

All states must transition to the new formula by 2011-2012 to provide more comparable data between states and to give states a more accurate look at how high schools are performing. Oregon took the step early, state officials said.

— Paris Achen