Why doesn’t the school system teach us skills that we’re actually going to need once we graduate school?

Schools teach knowledge.  You parents are supposed to teach skills.

Excellent question! Perhaps they really don't you to succeed so you can be wards of the state.

Math-You learn core math knowledge that will be used in most careers that involve math, what you learn will be expanded upon in post secondary school.

science-many many jobs involve an understanding of biology phyics or chemistry.

social studies-You're welcome you understand something about society.

English-You're welcome for learning how to read and write.

It's the basic package to give everyone the skills to have any choice they want, don't you want to be prepared to do anything?

somewhere around the 1970s there was an ideological shift in our educational system that decided its function was to create happy, self-confident kids instead of critical thinkers and good citizens...

that...coupled with the Department of Education deciding to hand out money based on how well schools checked boxes off "to do" lists rather than the performance of their students and teachers...created a system that produced kids who were socially conscious and had strong self images, but were well behind their global counterparts in terms of maturity, academics and practical skill sets.

My school did teach things like filing taxes and writing a check.  The class was called "personal finance" if I remember correctly.  It was half a semester with the other half being dedicated to teaching basic computer skills / internet use (this was back in the late 90's / early 00's).

Reading Writing Thinking Math? I use all that in my job.

That's the Question Every student & Parent should ask !

I have NO damn idea what's the use of a + b +c blah blah blah in Real life 😒

Algebra is 100000% USELESS 

It does.  You have no idea what skills you'll need, but lucky for you, your ignorance on that point doesn't mean that what they're teaching you you won't need.

UPDATE:

Oh, you're a troll.  Write a check?!  You're not in school.  You're at least 50 or 60.  The only people in the world still writing checks are great grandparents.

It's not the school system's fault that you didn't pay attention.