The first thing any young person should know about engineering is that it is an applied science. Scientists are in the business of finding laws of nature. Engineers are in the business of using those laws and making products.
There are a number of different engineering fields available. I became a mechanical engineer. With a mechanical engineering background I could choose to be a manufacturing engineer, an aerospace engineer, heating, ventilation and cooling, or a robotics engineer. Other types of engineering careers include chemical, biomedical, packaging, civil, computer, electrical, industrial, material, and nuclear.
Every engineer will learn a little bit about different sciences. As part of my mechanical engineering courses, I took two semesters of chemistry, four semesters of engineering physics, a materials science course, and an Electrical engineering including some digital signal processing. There is a lot of math involved in engineering. I took five semesters of math--integral calculus, differential calculus, multivariable calculus, partial differential equations with linear algebra, and advanced calculus. Because engineering is involved with production, we also needed a semester Of engineering economics.
My school, which I believe is typical of many engineering schools that offer a broad range of majors, did not expect a matriculation into a specific field of engineering until the second year of school. One of our required courses was an engineering overview where we heard from seniors or grad students in each specialty. Engineering is a tough course of study in four years. A full time college student needs to take 4 classes per semester. Schools limit the class load to 6. Engineering students have to take at least 5 classes a semester and half the time they need to take 6. And these 6 classes are intense with homework, projects, papers, and labs. I took an additional semester to finish up my degree.
Kids need to be prepared for college level math and science classes. That means high school must include algebra, trigonometry, geometry, and precalculus. If you get through calculus in senior year, even better. The science classes must include biology, physics, and chemistry. A good SAT score is important. Even better is a desire to solve problems.
The bureau of labor statistics at the U.S. Dept of labor has a great summary of engineering types available and also job outlooks and projections as well as earnings information.