Complex sentence: Though educational reform occurred on a local level at various points throughout history, the modern notion of education reform is tied with the spread of compulsory education--education reforms did not become widespread until after organized schooling was sufficiently systematized to be' reformed.
Split into simpler sentences: Though educational reform occurred on a local level at various points throughout history, the modern notion of education reform is tied with the spread of compulsory education. Education reforms did not become widespread until after organized schooling was sufficiently systematized to be' reformed.