Fewer U.S. teenagers were added to payrolls this summer, but overall employment among 16- to 19-year-olds still managed to reach the highest level in six years, according to a new analysis of government data by outplacement firm Challenger, Gray & Christmas Inc. Employment among teens increased by 1.16 million during the three-month summer hiring season that stretches from May through July.  While summer hiring declined, the total number of employed 16- to 19-year-olds reached 5,696,000 in July, which is the highest number of working teenagers since 2009, when 5,962,000 teenagers were employed during the peak employment month of July.