I'm fairly new to music, I've had no actual theory lessons and have only recently started piano, but since the beginning I was aware of major and minor scales. I was under the impression that there were three minor scales: natural, harmonic and melodic, with natural being the same as Aeolian. However, both my piano teacher and a couple of my more musical friends claim that natural minor isn't actually a scale, and that it is just descending melodic minor. Is natural minor actually a technical scale, or is it just a simplification that isn't used classically?
It is technically and officially a scale. Has been recognised as such by examining boards, and used in their scale sections of exams. Yes, it is the same as the descending classical melodic minor - but there's also the jazz melodic which uses the ascending notes both up and down.
Incidentally, it is also called a mode. The Aeolian mode. Made up from the same notes as the Ionian mode/ major scale, but centring on the 6th note of that major scale. Enlighten teacher and friends!
Natural minor is definitely a scale!
With that said, you ask if it's "just a simplification that isn't used classically." In my opinion, the distinction between the three (and more) forms of minor is a huge oversimplification. Sure, occasionally you'll get nursery rhymes that completely fit in natural minor, but more complex music will rarely fit perfectly in any of the three forms of minor. Instead, the music of Bach and Brahms and Scarlatti (and so on) use elements of all forms.
So, again: natural minor is definitely a scale. But when it comes down to it, all of these forms of minor are simplifications.
Technically out of a classical harmony point of view, the natural minor refers to the descending form of the melodic minor scale and is not a scale as we would typically call it.
When modernist talk about the natural minor scale they are reffering to what is actually the aeolian mode, the confusion is natural though.