My son wants to replicate some experiments and try to grow plants in Martian soil for his A-level science project. I know NASA have managed to produce soil that mimics Martian soil, however I also know how expensive it is.

My question is, what is the closest proxy to real Martian soil that I can create in the kitchen using readily available supplies from builders merchants, garden suppliers, chemists, and supermarkets?

Many thanks in advance.