Instead of WWII they started to teach about The Great Patriotic War, which starts in 1941, when Germany attacks USSR. I heard many Russians deny WWII, since the first two years are full of shameful acts and nazi-friendly stuff.
WWII, its dates and events were all in history textbooks in Russla when I was in school (1995-2005) and they are stil there.
We do not teach about The Great Patriotic War instead of the WWII. For TGPW is the greatest part of the WWII, for obvious reasons, that is why it is tought in more deapth and has more hours than other parts combined.
As I recall from conversation, it's that the USSR did not jointly invade Poland with Germany; this is evidenced in the fact that they did not invade on the same day. Furthermore, the USSR wasn't even invading Poland; the USSR was striking West through Poland in order to protect Poland from Germany.
Not true. One of the commenters on this thread was nice enough to post the modern-day history book for the 9th grade. Unless you believe he went through the effort of redacting it, you will see that it contains details of USSR’s invasion of Poland in 1939, German-Soviet pact and its secret addendum, nature of the agreement to divide Poland and other countries between Germany and USSR, and so on. Factually it seems to agree pretty well with Western sources.
Orlov's history textbook don't even give it a glancing mention in latest editions. That one is more common in more lower tier educational institutes.
A more liberal Brandt's textbook, the one posted above, been heavily edited year after year to its current state where the pact, invasion of Poland, and whole of thirties was reduced to just few pages.
https://en.wikipedia.org/wiki/Great_Patriotic_War_(term)