The Russian diaspora and cult TV fans have moved to Telegram. Search for channels named or "Logos Boarding Subs." These channels often provide direct downloads of .mkv files with hardcoded English subtitles. This is the most reliable way to get perfectly synced Season 3 subs.
Believe it or not, the most active community for this show lives on VK (the Russian Facebook). Search for groups named "Закрытая школа (Closed School) with English subs." These groups often have pinned posts with Google Drive links to subtitle packs. Zakrytaya Shkola English Subtitles -