I have always been wondering if the memory of this phrase is another example of the "Mandela Effect", like the Monopoly guy's monocle.
It just sounds so plausible, as it is stylistically the kind of stuff that teachers often say and it fits so well as we all have first hand experience on how fast technology has progressed especially during the 00s.
But on closer scrutiny it just doesn't make sense.
And it was already pretty obvious to anyone really early that this wouldn't make sense.
During my middle-school years in the 80s, things like calculator watches already were the hype (had one myself) and widespread enough for school to have to establish rules to cover those.
Shortly after that, I remember credit-card-sized calculators that where intended to be put into your wallet to be common giveaways by banks.
And compact GSM mobile phones started to become increasingly widespread from the mid 90s.
I see only a tiny timespan that the phrase would have perhaps been plausible, maybe just ten or so years spanning from the early 70s to the early 80s.
And I myself am pretty sure that I first heard the claim and the phrase itself in some relatively recent (last 10-15 years) online posts, but never before.