A Moment with the Rebbe: Although davening at 770 was set at 10 o’clock on Shabbos, to allow for time to appropriately prepare, the Rebbe instructed Reb Efraim Volf that this time isn’t for everyone.
The Rebbe set that davening at 770 should begin at 10 o’clock on Shabbos, to allow for time to appropriately prepare for tefila, through learning and contemplating Chassidus.
However, this wasn’t for everyone. In a 5734 (1974) yechidus with Reb Efraim Volf, the administrator of Chabad mosdos in Eretz Yisroel, the Rebbe directed him regarding the Beis Sefer Limelacha vocational school:
“At this mosad, davening should start no later than the time of reading Krias Shema. Since the students learn Kitzur Shulchan Aruch, they wouldn’t understand why davening doesn’t begin at the proper time.
“A yeshiva bochur, who is capable of learning Chassidus for two hours, understands why according to Chassidus davening should start later. But not a student at a vocational school. Especially the younger classes. Regarding the older classes, if indeed they could learn for two hours, and none of them waste their time, they could begin davening at ten.”
(For the full yechidus see Halperin Teshurah, Tammuz 5762)