Complex sentence: During some of this period, Alan Carney was the headteacher followed by Ivor Buckley (who was part of the directorship at Lancashire County Council) up to its closure in 1991 whereby the castle lay empty for a period of 6 years.
Split into simpler sentences: During some of this period, Alan Carney was the headteacher. Following the school's closure in 1991 the castle lay empty for a period of 6 years.