If I am not mistaken, in soviet time study of Ukrainian in school was also imposed also in Russian schools in Odessa.
In Donetsk and Lugansk now the only official language is Russian.
In Crimea they have also Ukrainian and Crimean Tatar as official languages, and they "can" have schools in Ukrainian (from my understanding at least up to kindergarten and primary school level) but I do not know if there is any actual request for it.
If I had to think something for western Ukraine after the SMO (either as a Russian protectorate (à la Puerto Rico) or as various Russian oblasts or republics),
I would say that Russian will be the official language, Ukrainian (better call it Malorussian) should be one of the recognised regional languages (as Hungarian should be as well in Carpathian Rus (former zakarpatia oblast).
But knowledge of Ukrainian (Malorossian) should not be mandatory, just an option.
Schools should be in Russian, with the possibility to have a certain amount of them Bilingual, at least up to primary school, and in many high school malorossian should be offered as a optional second language.
(So first language (and language of most subjects) Russian, and for second and third language the high school students should have the possibility of choosing between the regional languages and important foreign languages (Ukrainian, Hungarian, Polish, Romanian, German, French, English, Turkish, Italian, Greek, Latin, etc).
University should be only in Russian.
I would not ban the speaking of Malorossian in public or even in government jobs, at least between individuals, as long as the people do not use it in official meetings or refuse to speak Russian to russian speaking people or to anyone that prefer using Pushkin's language.