The Miami-Dade school district and teachers union leaders have hammered out a tentative healthcare agreement as part of ongoing negotiations, officials announced Tuesday.

Healthcare makes up the second biggest expense — $408 million for 2012, second only to payroll — for Miami-Dade County Public Schools. The district and the union had to negotiate how to pay for an expected $65 million increase in healthcare costs for 2012.

The tentative deal, subject to ratification by Miami-Dade’s 20,000-plus teachers, calls for some increases in the amount they pay for healthcare. The amount of the increase depends on a teacher’s pay scale, which benefits he or she chooses and the number of dependents.

Increases in dependent coverage could range from $80 to $2,000 a year.

On Friday, district officials and members of the United Teachers of Dade will return to negotiations. On the table: salary, the other major piece needed to broker a new contract.

Miami-Dade Superintendent Alberto Carvalho called the deal on healthcare a “landmark conceptual agreement.”

“While others continue negotiations, we can proudly say we got somewhere, even though these are tough times,” Carvalho, flanked by Karen Aronowitz, president of the United Teachers of Dade, and Perla Tabares Hantman, chair of the School Board, said at a news conference Tuesday.

Aronowitz said that a working group will continue to meet to develop a long-term strategy on health insurance and wellness. “We know that this is not a short-term problem,” she said

The deal arrived at the same time the Miami-Dade County Commission tackled healthcare issues and narrowly avoided layoffs of hundreds of employees. The proposal also follows the district’s transition two years ago to a self-insured program, which resulted in $100 million in savings.

Key parts of the proposal include:

•  Continuation of the free healthcare insurance option for employee-only coverage

•  Changes in the plan, including a limited pharmacy network that provides cheaper prescriptions and a specialist network, would save $28.3 million

The Miami-Dade School Board would pay the increases for the first quarter of this year, amounting to $16 million

•  The district and employees would share paying the cost increases expected for dependent coverage

•  Teachers could participate in an expanded wellness program that involves a health risk assessment. It’s meant to identify health issues early on, help employees improve their health and save money long term.