The Previous Rebbe learnt Shichta in Lubavitch, in 1908, by the local Lubavitcher Shchita teacher, Rabbi Shlomo Chaim Kiton. See Zikoron L’Bnei Yisrael, p. 10. Rabbi Alexsandar Sender Yudasin relates in his sefer HaLekach v’HaLibuv that in 1905-1906 an announcement was made in the yeshiva Tomchei Temimim study hall. Anyone that would like to learn shchita should submit their name for Rebbe Rashab’s approval. About twenty students signed up of which some of them the Rashab crossed out. It was known that if a student in Tomchei Temimim wanted to learn shchita he needed to fulfill the Shulchan Aruch’s condition. This was “having lots of yiras shamayim,” awe of G-d.