Aging school buses may go on the auction block, classroom computer purchases may be postponed and thermostats in some of Idaho's public schools could be set lower.

Officials are looking for ways to cut spending to cope with a shortfall in public school support from the state.The public schools budget is expected to be $5 million short because the state Department of Education underestimated 1990-91 enrollment by 4,000 students. This could cut the amount schools receive for each classroom unit by $1,017 this year from about $40,000 to $39,000.

If the Legislature does not approve extra money to make up the shortfall, schools will have to cut spending. They're planning for it.

"Computers are one thing we don't want to cut in the classroom, but maybe we can do another year without," said Michael Bishop, superintendent of Sugar-Salem School District.

Sugar-Salem, which already has a $149,000 deficit, stands to slip $80,000 further into the red with the loss of state money.

Bishop said the district could sell surplus school property, delay textbook and computer purchases, lower thermostats and turn off lights to conserve energy.

Bishop said a 30-member committee of district employees is looking at ways to erase debt and the shortfall.

The financial pinch is so critical some districts are considering employee layoffs and dipping into reserve accounts.

"The only way you really save any money is to eliminate people," said Jim Smith, superintendent of the Salmon School District. "You either reduce programs or you go to the public and try to convince them that they need to make up the difference."

The Salmon District also was in the red, $85,000 in debt at the start of the school year, and expects to receive $63,000 than expected. "This is just another blow on top of what we've already experienced," Smith said.

Ken Schow, business manager of the Idaho Falls School District, said the the district has a reserve account it can dip into to cover the loss of $468,000 in state money. But he hates to do that, knowing that an emergency could come up at any time.

"The biggest problem I have with it is there are so many things that can happen during the year," he said. "This obviously would be a very counterproductive measure."

The Madison School District, which expects to receive $223,000 less in state money, has imposed a budget freeze. Superintendent Chris Mattocks said the district will not order any non-essential books and supplies and will eliminate non-emergency building repairs.

The district also may reduce staff travel and leave job vacancies unfilled if they open up, Mattocks said.