Complex sentence: The Senior school is located in Croissy-sur-Seine and the current head master is Dr Steffen Sommer, assisted by two deputy heads, two heads of Key Stage, and the Head of Sixth Form.
Split into simpler sentences: The Senior school is located in Croissy-sur-Seine. The current Headmaster is Dr Steffen Sommer, assisted by two deputy heads, two heads of Key Stage, and the Head of Sixth Form.