This jacket is quite simple to knit, the squares get smaller as you progress up the main part. The only tricky parts are the half diamonds at the front and top edges; hopefully my instructions will be clear enough.
The yarn I used is no longer available, but the Jarol one will give a similar effct. You can use any yarn that knits to the correct tension: I prefer to use 100% acrylic for kids’ clothes, as it washes easily, dries quickly and doesn’t itch. Don’t iron or tumble dry it though, and wash it at 30 degress C, or it will go out of shape very quickly.
You could ring the changes by making the diamonds in rows of different solid colours, with a plain or striped yoke and sleeves. Be creative!