For larger projects, Stephen's system of choice is the Tower Garden. Tower Gardens are aeroponic growing environments which require no soil. Tower Gardens are great because they're relatively compact (2.5ftx2.5ft), highly efficient, and only take 30-45 minutes to put together. The simple and replicable nature of the assembly process also makes it easy teach students how to assemble Tower Gardens.
Tower Gardens are also great because they make it really easy for students to identify which plants are theirs, which will increase engagement levels and encourages the students to take responsibility for their plants.
The Tower Garden by Juice Plus:

The Tower Garden has a twenty gallon reservoir at its base that stores a nutrient solution, and a small pump. The pump pushes the nutrient solution up through a small central hose to the top of the Tower Garden, and from there the nutrient solution drips down through the central "tower" using a special device that evenly cascades the nutrient solution over the plant roots that are exposed there. As the nutrient solution drips down the tower, it feeds the plants' roots and becomes highly oxygenated. This process is repeated on a continuous basis in order to provide oxygen, water, and nutrients to the roots of the plants.
Tower Gardens use as little as 10% of traditional growing nutrients & water and yield up to 30% more produce on average when compared to traditional gardening methods. Plus, because there's no soil involved, you can avoid the mess and cleanup associated with traditional growing environments. (There's also no bugs, or weeds!)

With his current Tower Garden installations, Stephen is growing
37 kinds of edible plants and flowers in one of his classrooms. He
even uses his Tower Gardens to grow fruits (strawberries!)
year-round.
Here's a helpful How To video for setting up your Tower Garden System: