Simplify the following text for a Grade 12 native English-speaking person.
Original: Following the 1957 Rome Treaties to launch the European Economic Community , the Convention on the Organisation for Economic Co-operation and Development was drawn up to reform the OEEC . The Convention was signed in December 1960 and the OECD officially superseded the OEEC in September 1961 .
Simplified: In 1960 , OEEC changed its name , and it became OECD : the Organization for Economic Co-operation and Development .