CAA has signed Arne Duncan, who resigned at the end of last year after serving as Secretary of Education since January 2009. He was one of President Obama’s longest-serving Cabinet members. During his tenure, Dunan helped to secure congressional support for Obama's investments in education — including the American Recovery and Reinvestment Act's $100 billion to fund 325,000 teaching jobs — increases in Pell grants, reform efforts such as Race to the Top and Investing in…