When you are at a young age (elementary or middle school years), it is vital to make sure that your foundations and understanding of topics are thorough and complete. All students should have strong foundations in the three most important school subjects.
Mathematics: Everything in the world involves math or numbers in one way or another and there is no way that it can be avoided. Whether it is the programming of a video game or the price of things at the supermarket, numbers and math are everywhere!
English: English is the international language of the world. Without good writing and speaking skills we would not be able to communicate effectively with others. Proficiency in English is necessary in almost all aspects of our lives, as we use it to learn, to communicate, and to think.
Science: Science makes up everything around us, from the air we breathe to the the food we eat! In fact, science has advanced us into the society which we are today. The value and importance of science is immeasurable, and will likely be important for the future of our Earth.
Each of these subjects will provide both elementary and middle school students the most important knowledge of school learning. In their everyday interactions, each of these subjects will be used in one way or another. One cannot emphasize enough the value of thoroughly and properly learning each of these subjects in order to achieve both academic and personal success in one's everyday life.