I know. Talk about a waste of time. Turns out to be 70,000 hours that each person spends in K-12 school. Add any outside school work and that could be closer 90,000 hours.
I thought your number was quite mindblowing but then I worked out that 70000 hours is about 8 years if you were there constantly, 24/7.. 90000 waking hours is over 15 years.
I worked it out at around 15-18k hours (depending on where you live and variations in school day length).
It isn't until fifth or sixth grade that you can really start finding a passion.
I'd say I managed to spend 5k to 10k hours on learning about technology and programming. I had to completely ignore high school. I literally slept through it. Teachers gave up trying to get me to try; I was also a social outcast.