On school assignment in the park

A group of high school kids took over the park on an assignment; they had teacher's instructions on how to identify certain old trees.

Some thought it was fun,  some were even very enthusiastic, others relatively bored. 

It looks as if the last group decided to take it easy. This group did not see the need to put in effort or energy. Did they bet on getting by or rather on sharing by their younger peers? 

Also, they might not have liked the idea of being photographed while on the job.... and just for this once, I did not ask!