The teacher divides the class into four working groups and gives the assignment and materials to complete the work. 

Students have to conduct research.

Any of them will focus on one theme as an expert. ​​

Topics:

- what it is pollution;

- which are the causes and the effects of pollution;

- the most polluting countries;

-  the most polluted countries.​​​​​​

After this first moment, the experts of the same theme come together to debate about what they found out. 

The teacher also supports the students to carry out the research.

Thereafter the original groups are makeup again. 

At this moment students learn about their mates' themes and build up a presentation together.  

Later, each team shares its presentation to the others.