The first thing I did was to spend an entire day at the scrap yard, selecting suitable pieces which were small enough and with no raw edges which would hurt the kids.
These were brought back to the studio, and displayed in a central place. The children picked up interesting pieces, and tried constructing objects or animals with them. Adult help was provided, if the children needed to bend a piece in a particular way, or cut part of it; though this was discouraged.
A welder was at hand and as soon as the children had finalised their piece, they took it to the welder, who put them together.
The following day, children painted their piece first with an anti-rust solution. When this dried, they used enamel paints to give colour to their sculpture.