Complex sentence: Monmouth School is the senior institution of the Haberdashers'Monmouth Schools,, and collaborates with its sister school, Haberdashers' Monmouth School for Girls, for certain activities such as drama productions and Sixth Form courses.
Split into simpler sentences: Monmouth School is the senior institution of the Haberdashers'Monmouth Schools. Together with its sister school Haberdashers' Monmouth School for Girls, they collaborate for certain activities such as drama productions and Sixth Form courses.