This paper reports the use of robots in teaching the essence of Science, Technology, Engineering, and Mathematics (STEM) to students from first grade to 12th grade. This STEM skills learning experience was developed gradually over 4.5 years and tested by over 350 students. Since the sample size is small and the time span is short, only limited statistics data is available. The main goal of this paper is sharing firsthand experience of using the same set of robots to teach students over 12 grades. This paper starts with general information of the LEGO Mindstorms EV3 robots, the basic methods, and the concept of STEM in very simple terms. This paper then explains how building and programming robots was implemented in different ways for different age and experience groups. There are 5 groups in discussion. The first group is the youngest and without any experience. The second group is older but without experience. The third group is older and with some experience. The fourth group is a group of middle school age (grade 5 to 8) students, mostly with some pre-exposure to robots. The last group consists of high school students. Each group is given an age-appropriate goal. It is observed that they have different challenges to conquer. While using LEGO Mindstorms EV3 (and the previous version, NXT) is well studied, having hands-on experience of building a learning path for students from first grade to 12th grade is of value. Finally, the expectation of education results in the future is touched upon.