What do we really teach high school students? Facts about fallen empires, how to perform math operations the average person never uses, and what’s inside common creatures are some of the commonly-learned things in high school. Yet most high schools are missing the most important course of all: personal finance.

It’s a difficult thing to learn on your own, but very necessary, and being pushed into the college world without knowing anything about personal finance will only harm you in the long run. Here are three things you probably should know, but were never really taught in high school or before.

1. There’s no such thing as free money.

It seems obvious, but it’s a deceptively simple statement that covers a variety of situations. This statement can keep you from being scammed, wasting your time, and getting your hopes up. For example, if you get an email about winning a lottery you’ve never heard of, it’s nearly always too good to be true. If you haven’t invested money into a lottery, why would you win it? Yet people still fall prey to these types of scams and divulge personal information.

Another example: meeting someone online who promises to help you out of a financial situation if you give them banking information. We’d all like to be rescued by our rich, foreign prince or princess, but this is simply too good to be true… yet it doesn’t stop people who don’t know this rule from being scammed out of the money in their bank accounts.

There are some low-effort ways to earn money, but for the most part, there’s no substitute for hard work. With a good work ethic, money will come easily to you.

2. There’s no direct value on time.

This is a myth many of us start to believe when we get our first jobs: retail, a gas station, or fast food are some common industries for students. All of them generally pay minimum wage, so you might be earning eight, nine or ten dollars an hour. It’s a short step from knowing that to starting to calculate the price of everything in this kind of fashion. Those two hours of studying? You could have earned sixteen dollars. That forty-dollar gadget? Wow, it represents five hours of work.

Stop that train of thought as soon as possible. Look into residual income, also known as passive income – book royalties, for instance. You can earn from work you’ve already done, and your only real limit on the value of your time is self-imposed. There’s often little difference between those who charge ten dollars for an hour of their time and a hundred dollars, except that the latter understand this principle and know that their skills are worth it.

3. There’s no point in wasting money.

Particularly for college students, the temptation to waste money is everywhere. You know how expensive a night out is, and a new outfit can be pricey. Yet, you justify these things because you need fun or you can afford it. The drinks will be gone in a day, the clothes worn out, but memories from using the money wisely can last a lifetime. Consider whether you’d rather have a $50 outfit or save $50 towards a trip to another country, or another interest you have. Often, the latter will win out as long as you place enough importance on it.

There are more principles of personal finance that every college student should know, but these are the basics that will help steer you through financial success as an adult.