Once the 17 teacher furlough days are subtracted from the school calendar, Hawai'i public school students will likely have the fewest instructional days in the nation.

Teacher furlough days, which begin on Oct. 23, will drop total instructional days in Hawai'i to 163, placing the state at the bottom of the list below North Dakota at 173.

Most states provide students with 180 days of school. Only 11 states offer less than 180.

Many teachers, parents and principals are concerned that the loss of instructional days will hurt student achievement. At least one school — Kaiser High — is considering using three of its six teacher planning days to add more instructional days back to the calendar.

"After those furlough days were announced, our teachers started talking immediately about possibly using the waiver (planning) days as school days," said Kaiser High School principal John Sosa.

Teachers will still have to vote on whether to give up those days, and Kaiser's School Community Council would have to approve the plan. If that happens, the school would submit a formal request to the Hawaii State Teachers Association and the state Board of Education.

Sosa said his school will vote soon on whether to give up three planning days. Each school gets six of these noninstructional days a year that principals typically schedule for teachers to take workshops, collaborate with each other or plan their curriculum. Kaiser has already taken or has plans for three of the days, Sosa said, but the other three could be brought back as teaching days.

There isn't a federal requirement that public schools offer 180 days of instruction, but it is the commonly accepted average. Thirty states have 180 instructional days, according to 2008 data from the Education Commission of the States.

Unless other states make more drastic cuts in their days, Hawai'i will likely end this school year with students attending the fewest days in the nation.

Seven months ago, Superintendent Patricia Hamamoto said the state Department of Education was in support of President Obama's shift in education policy that called for longer school days and longer school years.

But $227 million in budget cuts dealt to public education by Gov. Linda Lingle and the state Legislature instead forced Hamamoto and education officials to whittle the school year down to save money.

"If we get an infusion of cash, however the Legislature deems we get money, we would look to recommending to the board that we reduce the furlough days," Hamamoto said.

Hamamoto said the drop to 163 days doesn't violate any law.

"It's not in law. There's no law that says how many days kids go to school in Hawai'i," she said.

"We accept and acknowledge that there will be an impact on student achievement, to student learning. Every day is important especially when you're trying to ensure that we make our proficiency marks and targets."

Principals say the reduction in instruction days this year could result in lower scores on the Hawai'i State Assessment, the state's measurement of student achievement under the federal No Child Left Behind law.

'Aiea Intermediate School principal Tom Kurashige said students at his school have been making steady progress on the state's standardized test.

Eighty-one percent of 'Aiea's students were proficient in reading this year, compared with the state average of 65 percent. Likewise, 58 percent of 'Aiea's students were proficient in math, compared with the state's 45 percent.

"Just looking at this from an academic standpoint, our kids cannot afford to lose any days," Kurashige said.

"We're going to try the best we can because I believe we have very committed teachers, but to be honest, making up for those days will be tough."

Students will have eight days less instruction in this year's second semester, typically when schools prepare for and take the Hawai'i State Assessment.

There were a total of 91 instructional days in the second semester last year. There would have been 93 this year, since both spring break and winter break were decreased by one week each. Furloughs, however, cut the total instruction days in the second semester to 83.