you can search the web to find the source is wikipedia [The Encyclopedia Judaic is apparently not available on line]
"According to Encyclopaedia Judaica, one assertion that was commonly made by many Jews of Salonika was that Kemal Atatürk was of Doenmeh (crypto-Jewish) origin. Many of Atatürk’s religious opponents eagerly embraced this view."
^ Gershom Scholem, "Doenmeh", Encyclopaedia Judaica, 2nd ed.; Volume 5: Coh-Doz, Macmillan Reference USA, Thomson Gale, 2007, ISBN 0-02-865933-3, p. 732.
Also on wiki:
" he attended the Şemsi Efendi School (a private school with a more secular curriculum) at the direction of his father. "
For the record retard, Semsi Efendi School is a Jewish Donmeh institution.