Obviously as adults we know that not everything we learn in school is used in real life, but 12 year olds have a different view because why spend time in a boring classroom when you could be doing something you like? "Why do I have to learn this? Why can't I use a calculator?" etc. Especially now we carry calculators around with us all the time.
What a good teacher should do is show that there's a path from learning to career success that is a bit more robust than the typical good grades -> college -> job.