14 year-olds using matrices

Coming up soon is the Qiskit Global Summer School which is something I'm suggesting some of my students attend. 

I was wondering whether at least some of it might be far too elementary for them, as the summer school is open to students aged 14 and over, with a prerequisite of knowledge that attendees know some basic maths including matrices.  One of the co-supervisors I was discussing this with, who is a bit younger than me, commented that he'd never come across a 14 year old who knew about matrices, which reminded me that today's students indeed don't come across them at that age. 

I happened to have on my desk a copy of Book 4 volume 2 of the School Mathematics Project textbook that I used at school.  Indeed, it has a stamp in it of my secondary school, and it is presumably a copy I should have, but didn't, give back to them after using. 

Here's a picture of the first page, the start of chapter 11 (it being volume 2, after all)

 Its opening sentence is "we saw in Book 3 how a matrix could be used to represent a transformation ..." so matrices were obvioulsy introduced no later than book 3, possibly eariler.  Inserted into this book was a folded timetable for my 3rd year (Y9 in current terminology) timetable, so I suppose I used book 4 volume 2 in that year.  Clearly, I was a 14 year old once who knew about matrices.  Being taught them then was so matter of fact that I never thought much about it.  There was a simple enough rule for multiplying them and that was effectively all that one needs to learn about matrices to use them.  Applications, such as using them for geometrical transformations, is another matter, and one can find ever more esoteric and advanced applications, but the basic properties are really rather simple.  Of course, I am the sort of person who ended up doing a PhD in theoretical physics, but the educationalists of the time presumably thought matrices a perfectly wholesome activity for 11/12 year-olds.