Simplify the following text for a Grade 9 native English-speaking person.
Original: Then , with the British proclamation of Elizabeth II 's accession to the throne in 1952 , the phrases Commonwealth realm and Head of the Commonwealth became established , deriving from the words that declared the monarch as `` of this Realm , and of her other Realms and Territories Queen , Head of the Commonwealth . ''
Simplified: Usually it is Queen of ( realm ) and Her other Realms and Territories , Head of the Commonwealth .