The California State Teachers’ Retirement System, the second-biggest public pension in the U.S., said its investments returned 13.5 percent in 2012 on gains in stocks, private equity and real estate.

The $158 billion fund’s calendar-year earnings missed its target of 15.4 percent, it said in a statement. U.S. stock holdings rose 16 percent, while bonds returned 6.1 percent. Real estate earned 13.5 percent and private equity was up 14.6 percent, according to the statement.

Pension costs for retired public employees are straining governments from California to Rhode Island. Calstrs, as the fund is known, had assets to cover just 69 percent of projected liabilities in fiscal 2011, according to data compiled by Bloomberg.

The fund earned 1.8 percent in the fiscal year that ended June 30, below its 7.5 percent assumed rate of return.

The California Public Employees’ Retirement System, the largest U.S. pension at $254.1 billion, also earned about 13 percent on invested assets last year.