Materials for the lesson

3 matchboxes filled each with coffee, sand and cotton (according to the book or different ones according to the teacher).
A small scale for small objects. (Kitchen scale, electronic if possible). This is the Catwalk-Scale where all the objects will pass to weight themselves.
Some sticky-tape or a sticker.

The teachers Bell.

Layout of the classroom

The desks at their normal position. Only one desk in front of all the others with space for the children to walk around it. Behind it and facing the rest of the class the teacher and 3 judges will sit. Three children that will alternate as well as the matchboxes.

1^st Phase

 The teacher asks the children to get an item out of their bag and choose one of them. The selected item will pass from the Catwalk-Scale and its weight will be found/recorded.
Pencils, pens, erasers, books, writing books, a sandwich our mother gave s from home . Cookies, chocolates etc come out one at a time and wait passionately to be weighted. We will find out who is heavier and who is lighter (we avoid term such as first, second or fat, skinny for obvious possible discrimination reasons)

2^nd Phase

The teacher places the scale on the front central desk.
He/she presents the three judges: the match-boxes with the coffee, the sand and the cotton and gives them to three children of his/her. The matchboxes are open so we can see what is inside. The three students hold with both hands the boxes comparing which is one lighter or heavier. Then they weight them on the scale and find their exact weight. The sand is the heavier and the cotton is the lighter. Then the boxes close. The three judges (boxes and children) stand on one side of the catwalk-desk and all the other students will parade before them. One by one all the children pass from the desk and weight their objects. On the other end stands the teacher and supervises the action. One of the children puts a sticker or a piece of paper-tape on ever object writing its weight as the scale said (this can be done by the teacher o a student).
The teacher can also choose to alternate the three student judges.

3d Phase

After all the children are done weighting their objects, they sit at their desks with the objects in front of them, with the weight written on them.                          The teacher asks randomly a student: What is the weight of the object?  (Answer). The teacher asks who has a heavier item and who has a lighter item from the first object. (children raise their hands, answers are given according to the weight and sticker). Slowly-slowly with all the questions and answers all the objects are classified from heavier to lighter. The objects are written on the board next to the students names. If there are any disputes, we weight them again. The three judges-boxes are in place.

4^th Phase

From all this classification a rich dialogue can emerge concerning the comparison of objects and their weight also compared to their size and form ( the eraser that is lighter from the text-book, but heavier that the pencil etc)

5^th Phase

Class continues. The match-boxes next to the children judges next to the Catwalk Scale have remained closed.                                                                                  The Teacher mixes them up so as not to know where is what.
The children are called to guess on their own and by their hands the three match-boxes and find –only criteria their weight- what is inside (naturally the heaviest is the sand and lighter the cotton but is is tricky sometimes as the size doesn’t always relate directly to the weight).