Simplify the following text for a Grade 6 native English-speaking person.
Original: After the death of Louis XIV and Guillaume-Gabriel Nivers , he succeeded the latter at the organ of the church of Saint-Sulpice and the royal house of Saint-Cyr , an institution for young girls from the poor nobility .
Simplified: He also had a job at the royal house of Saint-Cyr , which was a school for young girls from the poor nobility .