WHEN PUBLIC officials spend tens of millions of dollars of taxpayer money, they must behave like professionals, leaving no doubt decisions are based on merit rather than personal friendships.

For that reason, we are stunned by the continuing revelations about the relationship between Mt. Diablo School District Superintendent Steven Lawrence and Chevron, which is vying for the district's $70 million solar installation. It leads us to question his judgment on district policy and on the awarding of lucrative contracts.

In the spring, Lawrence championed the district's successful Measure C campaign to issue $348 million of bonds for school construction and upgrade projects. Unfortunately, Lawrence didn't seem to care how much the bond repayment would cost property owners.

It wasn't until we insisted on the numbers that they were produced, revealing an exceptionally pricey repayment schedule. The shocking total cost -- $1.87 billion in principal and interest, or more than five times the amount borrowed -- was never included in information provided to voters.

It should have been. The superintendent had an ethical responsibility to distribute the numbers to the school board and the public before the bond was placed on the ballot -- and to the voters before they made their decisions. He never did. It seemed at the time that Lawrence was an administrator too deeply enmeshed in the politics to provide the objective analysis central to his job.

Now, however, it seems that there might be more at play.

A key selling point for the bond measure was the solar program, which is supposed to reduce the district's energy costs. The savings are to be diverted to the general fund rather than used to pay off the bond debt. After the election, the district seemed headed toward awarding the contract to Chevron without competitive bidding until Bay Area News Group started asking questions.

It turns out, as education writer Matt Krupnick previously reported, that Lawrence had private meetings at his home before the election with Chevron officials. Now we learn from Krupnick that Chevron also took Lawrence for drinks at Oliveto, a high-end Oakland restaurant. And Lawrence solicited golf discounts in Lake Tahoe for his friends from Jim Davis, president of Chevron Energy Solutions.

The discounts were worth nearly $200. The drinks, assuming it wasn't Dom Perignon and that Lawrence isn't a lush, also probably weren't worth a lot. That's not the point. The point is that it crosses ethical boundaries. Lawrence must maintain an arm's-length relationship with prospective district contractors. Receiving them at his home and accepting drinks from them at fancy restaurants suggests a too-cozy relationship. Soliciting financial favors from them is inexcusable.

We expect better from a school superintendent. Lawrence owes the community an apology. He should recuse himself from participation in the bidding process for the solar project. And Mt. Diablo trustees need to establish a set of ethics guidelines that remove any hint of impropriety from district business practices.