A search for C* Siwek came up with only one girl--Cyrla. The name was a close match and Cyrla was born in 1930, which would have made her the right ae to attend School #8A.
Cyrla had a father, Zelig (b. 1893), and two possible candidates for a mother: Rojza (b. 1894) and Golda (b. 1907), although I'm inclined to think that Rojza is the mother and that Golda is another female relative (but that is just speculation.) Cyrla also had two siblings, Laja (b. 1923) and Jakub (b. 1928).
Golda either moved or was deported on July 24, 1944, although there is no deportation date listed in secondary sources for this date. No deportation information is available for any other member of the family except Cyrla, who died of unknown causes on April 5, 1943.