No one makes that assumption. We know from copious hard evidence that humans and modern apes are closely related, and from more limited hard evidence that there were other animals with features similar to both humans and apes long ago. More recent human ancestors were not apes (they were more human-like), and way distant past ancestors were not apes (they were before even prehistoric apes existed), and none of our ancestors were modern apes (which have evolved into their modern forms since our last common ancestors with them, and those common ancestors were not apes as we know them today). Some human ancestors were prehistoric ape-like animals.
Teaching well-established scientific knowledge in schools is essential, and about as far from criminal as it's possible to get. Your "all human species ancestors are some kind of ape" is not well-established scientific knowledge, but your faulty assumption of how you imagine others' knowledge to work.
You seem to be starting with the assumption that evolution isn't real (based on a primary school reaction?!), rather than deriving the knowledge that it is real from the evidence. (Yes, I have actually done this. I had a summer job deriving evolutionary relationships directly from genetic data. It's not difficult, and the connections between species just pop out of the DNA sequences with a bit of maths.) Evolution wasn't just made up, it was figured out from the evidence, just like gravity, electricity, chemistry, etc. Like all scientific fields, our knowledge of it is not complete (and never will be).