I was in primary school in the 80s. Maybe I just went to a really shitty school. They did it to my sister too, I asked in the family group if anyone else who went to that school wasn't taught maths, and my mum admitted none of us where and she knew we weren't but she believed the teachers when they said we couldn't do it because she was bad at maths.
My sisters didn't play with shapes and water. They played snakes and ladders with parent volunteers because it helped them learn to count 
I mean, maybe it did, but counting up and back from 6 was never going to prepare them for secondary school maths, was it?
And I don't think I know a single network engineer who has ever subnetted by hand outside of an exam, even the ones with degrees in maths, because why would you? Even if you are Einstein, doing it by hand is going to take longer than punching the numbers into a calculator.
I did say this to my maths teacher last week, who asked what we would do if the internet was down and we had to do it by hand! If the entire network in the whole building is down, including the wifi, we have bigger issues than which client is on which subnet 
I'm in my chosen profession now but, what happens is my contract ends or I'm made redundant, and I can't get back in at the same level even though I have experience because I don't have the certs. A lot of the time, my CV doesn't even get past the AI scanner. So I take a job at the next level down and work my way back up, and then the same happens again. I'm not getting any further ahead because I keep having to start again from the beginning, if that makes sense?