As for ID or creationism, if it has a valid description of origins, then people should be made aware of the differing theories.
By all means, let's teach ID and/or creationism as failed hypotheses, just like we teach alchemy and astrology as failed hypotheses. A theory is basically what you have left after you throw out all of the failed hypotheses. ID and creationism have failed every test, so all we have left is evolution, which has passed every test.
I'm saying we don't know; we have no reason to think they ever did.
You discount any historical documents mentioning their existence?
I wouldn't teach in schools that unicorns "might have" designed the universe based on legends about unicorns.
You discount that the mass number of extinct species did not include them?
Are you suggesting that we should teach in schools that unicorns "might have" designed the universe and then became extinct? If we're going to teach every possibility that remote, we'll have to extend the school year.
All theories should be mentioned. In the case of "the origin of species" there is only one theory - evolution.
Creationism is at best a failed hypothesis. It has failed every test concerning the age of the earth, the relatedness of species, etc. (Note that the age of the earth is not directly related to evolution but it is a creationist obsession.)
Learning is not an adventure if someone is force feeding.
It's a cute saying that "learning should be an adventure" but it isn'r really practical for an education system. Given the option, most children would do most of their adventuring on the playground instead of in the classroom, so a certain amount of "force feeding" is necessary.
The problem with being "self-educated' is that there is no discipline. There is nobody to "force" you to look at the things you need to know instead of just the things you want to know. That's why people who are "self-educated" tend to fall for nonsense like creationism - they've chosen to look at only one side.
A proper education system "forces" students to look at all sides. In the case of creationism, if it is presented honestly, the students will see for themselves that there is nothing to it. There is, indeed, nothing to teach.
Or they could have been lumped together in a global flood?
We could definitely have the children investigate that possibility. First, take them outside to look at the leaves on the ground (since school conveniently begins in fall). Would they expect all of the leaves to come from one gigantic tree or from the many ordinary-sized trees that they see around them?
Then have them think about whether organisms that are killed by a flood are likely to have been killed by one gigantic flood or by many ordinary-sized floods that they see on the news.
I think you'll find that letting children make up their own minds is the last thing that creationists want.
In either case the answer to the thread Q is more about method of educating rather than what should be taught, don't you think?
Well, you suggested that the children should be taught by allowing them to make up their own minds. I've been pointing out in the last couple of posts that if children do make up their own minds, they're quite likely to reject creationism (which is quite frankly, stupid).
If you want creationism to survive the education process, the only method that will work is hiding the truth.
While I am sure of a global flood, I don't know how these deposits took place.
I happen to know that my house was built in 1957. I have lived in this neighbourhood myself since 1962, so I know there has been no major construction on this block since then. If a book claimed that my house was built in 1989, what should I conclude? That the observational evidence is wrong and the book is right?
We know that the Dover cliffs are much, much older than 6000 years. We also know that many other formations are much, much older than 6000 years. Some of them, such as the cliffs, simply could not have formed in 6000 years, according to the laws of physics.
So we know that the earth is more than 6000 years old.
We also know, according to the laws of physics, that the Dover Cliffs could not have formed during a one-year flood.
It may be possible to maintain a belief in a 6000-year-old earth and a one-year Flood despite the facts, but that belief has no more place in our schools than a belief in flying pigs.
But you would also disagree with a book that claimed your house was a million times older, and that it took that long to build.
The point is that the house must be at least as old as its oldest part. If the concrete foundation takes several days to cure, you can't reasonably conclude that the basement was dug this morning. It could have been dug last month or twenty years ago or a thousand years ago. It can be older than the oldest (known) part but not younger.
That's why a young earth is a non-starter. It would be a disservice to our children to teach them otherwise.