Check the RSB web-site at: http://www.rspb.org.uk/advice/helpingbirds/nesting_mallards/index.aspx
It includes this information: "Mallards and their nests are protected by the Wildlife and Countryside Act 1981, which makes it an offence to intentionally kill, injure or take any wild bird, or to take, damage or destroy its nest, eggs or young.
Therefore, it is important not to chase away a duck that has started nesting, since she must be allowed access to her nest. If you find a nest full of eggs, you must not interfere with them. "
The boys would appear to have been breaking the law and could have ended up in the Magistrates Court.
Does anyone from the village school(s) monitor this forum? Alternatively, could the person who observed this illegal behaviour get in contact with the appropriate school, to ensure that the schoolchildren know about the laws that protect wild birds and the environment?