Every woodworker needs a couple of levels. You probably won’t need one of the 6-foot levels used in construction, but 48” is a good length for many of the woodworking projects you’ll do. Usually, you’ll also need an 8” level too, usually known as a torpedo level. You’ll check the level and plum of your construction. Level means horizontal, and plumb is vertical.
Then, beginning several decades ago, shop classes began to be removed from secondary curriculums. With the decrease in educational funding, and increasing emphasis on standardized testing, schools began to cull electives, institute stricter graduation requirements, and focus more on college prep academics and the subjects necessary for passing state exams. There wasn’t money or time to maintain tools and sawdust-filled workshops, and one by one school districts dropped their shop classes, figuring that students who wished to pursue trade skills could do so later at a vocational college.
Since money and space are usually in high demand, you want your purchases to make sense and work for you as far into the future as possible. To do this, the focus should be how to expand your capabilities rather than getting one project done quickly. With this in mind, and based on what I've learned over the past three decades, here's how I would proceed if I were starting over now.
In a full-time program, the instructor can start at the beginning with design instruction and the classic project to flatten and dimension a board four-square using only hand tools. In a part-time program, where you only have students for a few hours at a time and their interest and passion for woodworking ranges widely, you need to get them working on something tangible as soon as possible. Many of these students are here just to try something new or as a way to get out of the house. They have no intention of doing woodworking as a career. In fact, they have perfectly good careers as doctors, lawyers or CEOs of major companies. They did not just pay $400 to "flatten a board." Most of them would look at the board and say it was just fine the way it was or maybe they would wonder why you didn't just buy it that way?
Thickness planer. A thickness planer is used to fix surfaces of imperfect wood. If you are picking up less than perfect wood from the lumberyard, wood with some surface defects, a planer will let you fix that wood in the quickest time. A thickness planer pays for itself quick as it allows you to buy cheaper wood that doesn’t have perfect surfaces and fix it yourself. Be careful though. You loose wood during planing. So the remaining amount of wood still has to be worth the price you paid for it.