This educational video made by Mediterranean Cetacean expert Jessica Alessi explains differences between cetaceans and fish and uses her actual photos and videos to identify different species that are commonly found in the Mediterranean, link. 

Answer: Fin whale, Sperm whale, Cuvier's beaked whale, Long-finned pilot whale, Risso's dolphin, Common bottlenose dolphin, Common dolphin, Stripped dolphin.

A one question activity that shows how scientist identify cetaceans when monitoring the population, link. Made by the Center for Coastal Studies - Provincetown, who have been working on science that matters for over 50 years. 

This powerful yet worrisome resource shows the endangered status of Cetaceans, link.  The Cetacean Specialist Group (CSG) uses scientific data to understand the threat level of different species and with graphs and infographics help share the knowledge. The International Union for the Conservation of Nature (IUCN) has many projects of which one of them is the Conservation Status that you may have seen on different websites regarding a specific species. Working under the IUCN are many "Specialist Groups and Task Forces" that are focused on a specific category, such as Cetaceans. 

This detailed and extensive text, also by the IUCN, is beyond the level of a primary school students, however, it has numerous interesting graphs and images that can be shared as a supplementary resource to aid discussion and focus only on the Mediterranean Sea, link.