Simplify the following text for a Grade 25 native English-speaking person.
Original: From 1956 on , he studied philosophy and sociology under the critical theorists Max Horkheimer and Theodor Adorno at the Johann Wolfgang Goethe University Frankfurt am Main Institute for Social Research , but because Horkheimer had asked Habermas to make some changes to his dissertation , or final project which Habermas did not want to do , and Habermasâ s thought that the Frankfurt School was not correct in its views of modern culture , Habermas left the Frankfurt School and he finished his habilitation , or highest academic degree , in political science at the University of Marburg under the Marxist Wolfgang Abendroth .
Simplified: From 1956 on , he studied philosophy and sociology under the critical theorists Max Horkheimer and Theodor Adorno at the Johann Wolfgang Goethe University Frankfurt am Main Institute for Social Research , but because of a rift between the two over his dissertationâ '' Horkheimer had made unacceptable demands for revisionâ '' as well as his own belief that the Frankfurt School had become paralyzed with political skepticism and disdain for modern cultureâ '' he finished his habilitation in political science at the University of Marburg under the Marxist Wolfgang Abendroth .