She wasn't dismissive of digital-airbrushing; instead, the reasons for us not doing any digital-art in art class are the ones you'd reasonably expect:

1. The #1 reason is cost: in money, time, training, et cetera: physical hardware purchases, Photoshop or Painter licenses - and needing to keep those renewed - sending all the art teaching staff away for training on the software and digital-painting technique themselves - and more besides.

2. Art, as taught in middle-schools/lower-secondary-schools to children - not working professional adults - is concerned with breadth, not depth: digital-painting is a specific and narrow technique when compared to the applicability of teaching art-theory things like perspective, shading, etc.

3. The practical and technical aspects of producing visual-arts, including on a computer, are already taught in the elective graphic-design class in upper-secondary (while our lower-secondary art class was mandatory); she could probably tell that I was motivated more by my ego-driven need to demonstrate my own 1337 Photoshop skillz to others than any actual belief I had that everyone in the British economy needs exposure to Wacom and Photoshop and receives training so they can all have their own DeviantArt account.

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So now, in the event that some kids' art teachers or others are being broadly dismissive of digital-painting then they're likely pointing to the impracticality of it being a taught subject in mandatory education in public schools - and not that it's any "less" of an artform. Instead, I think it's worth comparing digital-painting to its own predecessor in (real-life) airbrush painting: just like digital-painting it requires its own hardware (think: expensive); while it can produce unique eye-catching results doing-so requires extensive practice; and is just as impractical to teach to large (25-30+) sized groups of kids en-masse; and won't help you appreciate a Monet or Renoir any more than a semester learning Photoshop would.