MT. DIABLO school officials never provided voters key information that would reveal the tremendous cost of the district's bond proposal on the June ballot.

To understand the exorbitant price tag of Measure C, think of a home mortgage. If you were to borrow $348,000 to buy a house using a conventional 30-year mortgage at 5 percent annual interest, you would end up paying $672,530 in principal and interest over the life of the loan. In other words, you would pay back roughly double what you borrowed.

In contrast, with Measure C, district officials seek permission to borrow $348 million to fund school construction and upgrades. But officials haven't told voters that they plan to stretch the repayment out over more than 40 years with most of the pain coming on the back end. To cover the principal and interest, property owners, by one estimate, would have to pay $1.87 billion in taxes, or more than five times the amount borrowed.

"This is an expensive way of financing construction projects," admitted Walnut Creek City Councilman Kish Rajan, one of the community leaders who signed official ballot arguments in favor of the measure.

It seems that even school officials didn't know the full expense. When Superintendent Steven Lawrence came to us last month seeking editorial backing for Measure C, I asked him what the total cost would be. He had no idea. Indeed, the district didn't generate the number until I asked for it.

There is no legal requirement for the district to crunch that number. But it seems to me that no public agency should be allowed to put a bond measure on the ballot without first computing and revealing an estimate of the total cost.

Clearly that wasn't a high priority at the district. In their quest to come up with a bond plan they could sell to voters, district officials and their financial consultant focused on devising a plan that was political salable rather than one that made good financial sense.

It's like the credit card company that tries to lure you in with the minimum monthly payment and neglects to mention that, at that pace, it will take you a lifetime to pay off the balance. Or the mortgage lender who offers low interest rates for the first few years to get you into a house and then clobbers you later with higher payments.

As smart consumers, we should realize there is no free lunch. We either pay now or we pay much more later. School bonds are no exception.

But we should be able to count on our elected and appointed officials — especially school officials — to be transparent about the costs. Unfortunately, as this case demonstrates, we cannot.

In their zeal to help our children now, backers of the measure would strap taxpayers with irresponsible debt they would still be paying off when some of those kids are starting to have their own grandchildren.

In addition to driving up the cost, the delay means the district will have less room to issue bonds in the future to meet additional building needs. And, in case there's any doubt, there will be additional building needs. District officials acknowledge that Measure C will only cover about half the projects they would currently like to complete.

The reason for the repayment delay is that Measure C was constructed so that property owners would feel minimal immediate impact on their tax rates. It's complicated because district voters approved an earlier bond measure in 2002. The tax rate limit on those bonds is $60 a year for every $100,000 of assessed value. The rate next fiscal year will actually be about $54 per $100,000. That means that, without Measure C, the owner of a home with a $300,000 assessed valuation will pay an additional $162 next year in property taxes to help retire the original bonds.

For the new bond measure, backers could have proposed increasing the tax rate another $60 per $100,000 assessed valuation. That would have been the fiscally responsible approach. But backers wanted to sell Measure C to voters by saying their maximum tax rate would not increase. The consequence of that is that the district would issue the new bonds in the next few years, but wouldn't make most of the payments on them until after the original bonds are paid off, in 2031. As a result, the new bonds would not be paid off until about 2052 under one projection by the district's consultant.

Delaying the pain dramatically drives up the interest. When I asked Jon Isom, the district's financial consultant for Measure C, he acknowledged how costly this scheme is. If voters were instead asked to increase the tax rate and started paying off the bonds immediately, the total cost of principal and interest could be held to about double the amount borrowed, just like our home mortgage example, instead of a ratio of more than 5-1.

There's another problem: Bonds for construction don't address the district's most critical problem. What the school system needs first is money for its day-to-day operations that have been shortchanged by the state budget crisis. For that, the district needs a parcel tax, an annual assessment to raise money for the general fund. The problem is that requires approval of two-thirds of the voters, a threshold the district failed to meet when it put a parcel tax on the ballot in May 2009 and only received 59 percent approval.

District officials considered trying again. But when polling showed they couldn't meet the two-thirds threshold, they instead turned to the bond proposal, which requires approval of only 55 percent of voters. It's like going shopping for a car when you need transportation, but buying a house instead.

However, a chunk of the bond money will indirectly wind up in the general fund. That's because district plans call for spending at least $60 million of the Measure C funds, about 17 percent of the bond money, to install solar panels throughout the district. Converting the school's energy source, the district estimates, would save more than $3 million a year.

That would make sense if district officials intended to use the savings first to pay off the portion of the bonds financing the solar installation. But that's not the plan. Rather the savings would go directly into annual operations. Taxpayers would be left to pay off the bonds.

District officials, led by Superintendent Lawrence, are proud of this maneuver (which also has not been disclosed in the official voter information). They see it as a way to generate money for current operations. Or, as Lawrence put it, "The bottom point of this measure is to focus on our kids that are in school today."

I'm sympathetic to the plight of California public schools, which are being strangled by the state budget crisis. It's a very serious problem. But this is certainly not an example of the fiscal responsibility we want to teach our children.

Daniel Borenstein is a staff columnist and editorial writer. Reach him at 925-943-8248 or dborenstein@bayareanewsgroup.com.