We are not told which school Mother Teresa attended.
Wikipedia tells us that Mother Teresa was born on 26 August 1910, in Üsküb, Ottoman Empire (now Skopje, capital of the Republic of Macedonia). Although she was born on August 26, she considered August 27, the day she was baptized, to be her "true birthday." She was the youngest of the children of a family from Shkodër, Albania, born to Nikollë and Drana Bojaxhiu. Her father, who was involved in Albanian politics, died in 1919 when she was eight years old. After her father's death, her mother raised her as a Roman Catholic.
So perhaps she attended a Catholic school after she was 8 years old.