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.