At KS1 and 2, use a box of straws as in the picture like an electron microscope. How many times do you think it is magnified? If you glue all the straws together then try to cut them with a hacksaw you can clearly see what happens to the grain - it frays and causes splinters.
Cutting at an angle will show how the grain appears in furniture.
Scraps from a timber merchant can be used at KS3 to make a letter opener showing pupils how material and form combine to make a beautiful object.
The letter opener can be finished with a high polish. GCSE students could start by asking what has mahogany not been used for? Make a ring or earring, something that will complement the beauty of the material. For homework or A-level, ask for some words on sustainability connected with mahogany. Mahogany now has to be farmed unless it falls naturally. Why do we buy illegally felled trees from rain forests? How can we find out about it?