I was born in 1947 just two years after the end of ww2 and went to high school during the sixties. I can't recall more than a passing reference to the extermination of 6,000,000 Jews. How can this be? I remember in junior high school drawing a swastika on my notebook thinking it was cool. Nazis to me meant nothing more than the other side we were fighting against. I grew up in Pennsylvania, was it different elsewhere in the country? It wasn't until I was grown and saw documentaries and read books about it did I learn about the atrocities that happened in Nazi Germany.
Both question and answer /comments appear very Americo-centric. I was born in 1949, just 2 years after the OP, and I cannot remember not knowing about the second world war and the atrocities. We did not study the war at school, but as someone said, it was not "history" - it was our parent's and older siblings lived experience. Whilst the word "Holocaust" was not coined until much later, I grew up with expressions like "looks like something out of Belsen" for someone very thin, and British cinemas showing newsreels of the death camps. Perhaps for Britain, being part of Europe, and for a time under very real threat of invasion and incorporation into the Nazi Reich, not to mention the Blitz, still scarring the landscape in my childhood, it was a more intimate memory - total war, involving every member of the community. I suspect this was not the case for Americans, except those who actually fought in it - who, indeed, probably wanted to forget it. Certainly for my British generation it was less history than still news - albeit yesterday's.
There appears to be an explanation in the book Generations by (the late) William Strauss and Neil Howe. It has to do with kinds of people, specifically generations, that became teachers immediately after World War II.
The older of these two was the so-called World War II generation. This generation provided the soldiers that beat the Nazis, but having lived the horrors of war, they didn't want to talk about it, least of all to their children. The younger of the two generations was born just before World War II, and was carefully protected from knowledge of "it," (that is, the war) when they were children. That generation was called the Silent generation.
It was only the Baby Boom generation, born (mostly) after the war, that was concerned with "causes and consequences" of the war. This was a very "loud," idealistic generation that "raised consciousness" in all aspects of American society, including civil rights. This generation became schoolteachers in the 1970s, (not 1960s), which is why the Holocaust became a hot topic at the time. It was a generation far enough removed from the war not to be directly affected, and therefore able to examine it objectively, yet close enough to feel a proximity to it.
Having been a compulsive reader of my (USA) school history texts, I can tell you that up until at least the 70's, very few went that far forward. My grade school texts (which were quite old) didn't really go past Reconstruction. This was probably plenty, because I never once had a teacher who managed to make it all the way through the text anyway. I don't believe I ever even had a school history course cover World War I events, let alone II.
As to why they ended there, that's arguably a good thing. Many people (even quite a few on this site) will argue that any event for which the majority of the active participants are still alive is not yet "history", but rather a recent event. Technically you could argue that anything for which any participant is still alive is not fully history. Its not really possible (or at least easy) to take a proper dispassionate historical view of events when you have first-hand knowledge of them at hand. Certainly if you throw in all the extra passions involved with parents in a school environment, it would be next to impossible to pull off properly.
In the 1950's and '60's, I think its inarguable that the events of the late 40's were still very much current.
Popular media of the time certainly picked up the slack though. WWII movies were a major genre back then, as were novels, histories (both popular and academic), and TV and radio works. This included works on the Holocaust, such as this mini-series from 1978. This list of Holocaust-themed films includes 11 US films from 1946 to 1967.
I understand in Germany the children were not taught about WWII during the 1950's, which led to many who do not believe the Holocaust ever happened. I went to parochial schools during the 1960's and we were taught of WWII in history, although it was not called the Holocaust. But it was not until 4th grade that we were taught more of the darker side of history and it was considered modern US history. And took US History in high school in the early 70's and learned of Dachau and Auschwitz. We did not learn of all of the particular concentration camps but knew there were many of them. But then again we did have Hogan's Heroes on Tv during the 60's, so although it was comedic relief it made it a bit easier to have talks about the war.
I also recall that the internment of American citizens was either barely touched on or simply ignored in HS history courses a few decades ago as was, for example, the Tulsa massacre in 1921. To be the devil's advocate: HS history tended to ignore unpleasant things. Columbus was treated as a great man also.