The Hillsborough County School District has achieved a record graduation rate and ranks among the top large school districts in the nation. Yet many of its schools inhibit rather than encourage learning because they are in such sad shape. Broken air conditioners, leaky roofs, lead in the drinking water - the schools are crumbling, and there is not nearly enough money to repair them or build new ones. As the state abdicates its responsibility to adequately fund public education, the only viable option is for Hillsborough voters to step up and approve a half-penny sales tax increase so kids can learn and teachers can teach in decent learning environments.The need for more money is obvious. For more than a year, the Tampa Bay Times has chronicled how air conditioners routinely fail across the school district. Students are sweltering in classrooms where temperatures pushing 90 degrees are forcing some students and teachers to go home sick. On the first day of this school year, more than half of the county’s public schools submitted maintenance requests to fix busted air-conditioning systems. In the first nine days of this school year, the problem only grew worse, as a staggering 1,533 requests were made to fix air conditioners, temporary chillers, water fountains and water cooling units. Beyond endangering health, the busted cooling systems disrupt classes, destroy equipment and damage classrooms.Air conditioners are just one problem. The district has a billion-dollar maintenance gap, thanks in part to a building boom two decades ago and a Florida Legislature that slashed property tax rates for capital projects during the economic recession and never restored them. The school district also shares responsibility for this crisis; it spent too heavily on a teacher training experiment and moved too slowly to cut costs and reduce a bloated workforce. Yet while the district has made progress in the past three years in shedding staff and controlling its budget, reducing expenses alone would not save nearly enough money to pay for needed repairs to schools.The spending plan sets the right priorities and fairly spreads the money from the half-cent sales tax. Roughly half of the $1.3 billion the tax would generate over 10 years is earmarked for air conditioning improvements. It still would take the district several years to complete overhauls at 41 critical schools, but the tax would get real money into the pipeline and accelerate the repairs needed to provide healthier learning environments.The second priority is to repair aging roofs. Tens of millions of dollars also would go toward a range of additional projects, from new plumbing, windows, fire alarms and floors to painting and weatherproofing. The work plan will protect the investments taxpayers already have made by extending the lifetime of facilities in the nation's eighth-largest school system. These buildings are community assets, serving as hurricane shelters and venues for major area sports, cultural and civic events. Every school would get money over time, and a school-by-school list of the projects is available at the district's web site, sdhc.k12.fl.us.The Hillsborough School Board acted hastily this summer in putting the tax on the November ballot. It could have built a stronger case by working longer to rebuild its finances and restore public trust before seeking a referendum. But the flawed process should not detract from the core issue at hand - the district's undeniable inability to repair and maintain its schools without a significant new revenue source. This is another state responsibility that has fallen to local government. Nineteen of Florida's 67 counties already levy an additional half-cent sales tax for school capital needs, while others - including Pinellas - have committed additional property taxes for school operations. Voters have wisely embraced public education as a priority even if their elected state leaders have not.The district has worked fast to get the referendum into reasonable shape. The 10-year tax is targeted to fill an immediate funding gap as the district pays down existing debt. That buys time for critical repairs until the district can free up tens of millions of dollars now going to mortgage payments. Fittingly, 85 percent of this tax would go for deferred maintenance - not new schools. Strict rules would limit the ability of privately run charter schools to tap the fund. And an independent oversight committee would meet publicly to ensure the money is spent as promised. That panel would be chaired by Betty Castor, the widely respected former legislator, state education commissioner and University of South Florida president. Hillsborough County Sheriff Chad Chronister would serve as vice-chair.Public schools reflect a community's values and its collective ambition for its children. Hillsborough voters should invest in the schools and ensure those buildings provide safe -- and cool -- learning environments. For Hillsborough County referendum No. 3 on a half-cent sales tax for school capital improvements, the Tampa Bay Times recommends voting Yes.