Slide rules?? AAAAAAAGGGGGGGHHHHHHHHH!!!
I personally wouldn’t allow calculators in elementary school, excepting perhaps for some advanced problems of some sort. But I agree that that’s where kids are going to develop most of their number sense, if they ever do. I think having a certain handful of basic arithmetic facts and experience in one’s head is good for speed and estimation. If you have to hit the buttons to know that 6x9=54, that’s gonna slow you down. If you can’t look at 653/7 and say, “that’s gonna clock in at a little under 100”, then you’re going to believe the calculator when you hit the wrong key and it tells you something really, really wrong.
OTOH, there are two classes I taught routinely with calculators (TI-83 in the years just after it first came out), and wouldn’t dream of teaching without it. One was pre-calc, and the other was elementary statistics.
Pre-calculus is all about understanding functions. I can’t think of a better way to build up experience with functions, fast, than to be able to use the calculator to plot dozens of variations on a function in the time that the typical student can plot one graph on paper, point by tedious point. If I want them to build up a sense that f(x)+6 moves the graph up six units, but f(x+6) moves it to the left six units; that 6*f(x) stretches the graph vertically by a factor of 6, and f(6x) compresses it horizontally by the same factor, then having them graph a bunch of variations, print them out, and tell me what’s happening is the best way.
And in statistics, perhaps my most joyful day as a teacher was the day I chucked the normal distribution table into the wastebasket. I used to burn three or four lectures each year, just teaching kids how to figure probabilities from the table, or work it backwards to get intervals from probabilities. What a waste! What I wanted the kids to be able to do was to understand when a situation called for a probability, an expected value, a hypothesis test, or a confidence interval, and which distribution or test they should be using. Once I had calculators in their hands, we were able to cover about 3 weeks’ more material in a semester, and in my opinion, the level of comprehension was higher.
When I was still teaching, I hadn’t really incorporated calculators very far into my calculus classes. At the time, calculus was still primarily about finding derivative and antiderivative functions, and few students had the TI-93 which was then the only ‘calculator’ (it had a QWERTY keyboard and kinda blurred the lines) that could crunch those out.
I’m not sure what the typical calc series looks like these days, but I hope it’s changed considerably, more towards a mix of fundamentals and applications. I’ve gravitated towards feeling that if I were designing a curriculum, I wouldn’t care whether students can calculate derivative and antiderivative functions, so long as they understand what they represent, and when confronted with a semi-practical problem, they can figure out what they ought to be taking the derivative of, and how to use that derivative to solve the problem.
That’s my 2¢; do with it what you will.