Denver Public Schools has quietly put the rest of its controversial variable-rate bonds with swaps on the market to sell as fixed-rate debt. Five years after issuing a 30-year, $750 million school pension bond that turned into a financial quagmire for the district, DPS is selling $519.8 million in fixed-rate, refunding certificates of participation (COPs), set to price during the week of April 15, according to an announcement Friday from Fitch Ratings. ... DPS "fixed out" — or issued debt at a fixed interest rate — half of the original $750 million in debt in 2011, and paid nearly $42...