A $548 million bond to upgrade Portland school buildings appears to be headed for failure, preliminary results suggest.

With about 70 percent of the vote counted, the bond so far has been rejected by 53 percent of voters in

.

Voters approved a separate property tax increase to preserve teaching jobs, early results show. In partial returns, that levy is ahead 55 percent to 45 percent.

May 2011 election results

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The bond is the biggest ever proposed in Oregon and would go primarily to fully renovate and update six aging schools and to build two new schools to replace worn ones. All 77 other schools would get smaller fixes such as updated science labs or a covered play structure.

Property owners would pay $2 per $1,000 of assessed property value for each of the next six years. That comes out to about $300 a year on the typical home in the district, assessed at $143,000.

The campaign in favor of the two tax increase drew more than $1.2 million in donations, mostly from construction companies, trade unions, utilities and others that stand to directly benefit from the building boom.

With partial votes tallied from the three counties that each include a portion of Portland Public Schools territory, as of 10 p.m. the bond had garnered 44.019 no votes and 39,806 yes votes.

There are still roughly 48,000 votes to be counted countywide, with most of those in Portland Public Schools, according to elections spokesman Eric Sample.

For Portland Public Schools voters to reject a schools money measure is highly unusual. The last three such votes were all heavily in favor of taxes for schools: 58 percent approval for a 1995 bond measure, 60-plus percent approval in 2003 for a temporary county income tax for schools and 63 percent approval in 2006 for a local-option levy to support school operations.