Simplify the following text for a Grade 8 native English-speaking person.
Original: Its poor conditions , Charlotte maintained , permanently affected her health and physical development and hastened the deaths of her two elder sisters , Maria ( born 1814 ) and Elizabeth ( born 1815 ) , who died of tuberculosis in June 1825 .
Simplified: The poor conditions of the school permanently affected Charlotte 's health according to her . She thought it led to the early deaths of her two elder sisters , Maria ( born 1814 ) and Elizabeth ( born 1815 ) .