This was the third of the three ideas I suggested in the orginal essay (see link to the right). This is not a duty on individuals as you might expect but a duty on local government.
If local authorities had a legal responsibility to ensure that everyone was an active citizen in the same way that they must ensure that all children attend school then the active promotion of citizenship would become a core activity instead of the marginal (or non existent) activity it is now.
It is even possible to imagine local councils being fined for failing to meet their citizenship targets in the same way as they are now if they fail to meet recycling targets.
However the duty was framed it would place an imperitive on local government to come up with ever more ingenious ways to educate and engage the local population. Departments of Citizenship would sping up in all local coucils an counter the tendency for (UK) local government to be dominated by administrative rather than democratic concerns