Property owners in the Portola Valley School District will be asked to tax themselves $581 per parcel to maintain the quality of the district's two schools.

The school board decided Wednesday to hold an all-mail ballot election May 7 on a measure that would extend two parcel tax measures totalling $458 a year and add $123 to the sum.

Board President Jocelyn Swisher said she felt confident voters would once again come through. "People in Portola Valley are proud to have such strong schools," Swisher said in a phone interview Thursday. "It's probably one of the most important investments people can make, to support the quality of our education."

The current parcel taxes -- a combination of Measure C, passed in 2004, and Measure D, passed in 2010 -- together generate about $987,000 a year, or 8.2 percent of the district's $12 million general fund budget, according to district records. A $123 increase is estimated to contribute $265,065 more per year.

If a May ballot measure is approved, the $581 amount would be effective July 1.

The tax money would be used to "maintain quality science, math reading/writing instruction; retain qualified/experienced teachers; minimize class size increases; support music/art programs; develop advanced programs in engineering and technology," according to proposed language for the ballot measure.

"The money is essential to our budget," Swisher said.

The Woodside, Las Lomitas and Belmont-Redwood Shores school district boards also are considering possible tax measures.

Email Bonnie Eslinger at beslinger@dailynewsgroup.com; follow her at twitter.com/bonnieeslinger.