Congress has given final approval to a bipartisan measure lowering student loan rates for now, only to hike them in just a few years. The interest rate for Stafford loans climbed to 6.8 percent last month after Congress failed to reach a deal to avoid the hike. Under the new measure passed by the Senate last week and the House on Wednesday, students will pay a lower rate through 2015, but then see those rates jump as they become attached to financial markets. The bill now goes to the White House for President Obama’s signature.