The Home Builders Association of Metro Orlando, which represents area developers, has sued the Orange County (Fla.) district to force the system to pay for all its new schools with a voter-approved sales tax. The trade group also is asking the court to lower the fees developers pay school districts to offset the cost of building new schools. The district says it is building the schools promised in a 2002 sales-tax election, but is having to use other money to cover the total cost. The home builders group says it is trying to make district leaders stick to their promise to build new schools with voter-approved money and relieve crowding at existing schools. District officials say the suit could derail efforts to improve dilapidated campuses across Orange County, and is a thinly veiled attempt to boost a stagnant housing industry.