OAKLAND -- The Oakland school district for years has relied on high teacher attrition rates and one-time funds to avoid the layoffs of tenured K-12 classroom teachers.

This year could be different.

A letter from Superintendent Tony Smith that was posted on the district's website Tuesday said a "significant" number of teachers, as well as nonteaching staff, soon will receive a notice in the mail that they might not have a job next school year.

The district also plans to notify all principals and some other managers that they might be reassigned to a new position in the fall.

"There's no denying that it will be disruptive," said Troy Flint, a spokesman for the school district.

But Flint said the uncertain funding levels for next year, combined with the evaporation of one-time funds, have left the district no choice.

"Basically, we've exhausted our bag of tricks," he said.

State law requires school districts to warn certain employees of the possibility of a layoff by March 15. Flint said that a specific number of notices has yet to be determined, but that it's likely to be in the hundreds.

A report issued by the nonpartisan Legislative Analyst's Office this week said without the $12 billion tax extension proposed by Gov. Jerry Brown, schools and community colleges could face cuts of about $5 billion. For Oakland, that could mean a loss of $12.6 million.

Read Katy Murphy's Oakland schools