Isn’t standing up when answering the norm? I grew up in ex-USSR in 90s/00s and that’s what we did. It felt totally normal and giving kinda a 1-to-1 connection to teacher instead of being a random voice in a classroom.

As for “helpful to adults”, it’s not exactly Soviet thing. All cultures/nations that were forced under Soviet rule had that mentality. And still have to big extent. Although there’s less and less automatic respect to adults/elders in last decade or two, it’s still there.