>  Using the modern 

> criteria for identifying a "public good," namely, (a) joint 
> consumption and (b) non-excludability of consumption for non-payment, we rule 
> out education from the list of public goods...
> James Ahiakpor


The rationale is that some elements of education provide a positive externality to society,
and this positive effect is joint consumption.
For example, if youths are educated to behave well, whereas otherwise they 
would be thieves and vandals, this creates a positive externality that many
benefit from at the same duration of time.

Or, if the public were educated in the basics of economics and thereafter 
avoid voting for taxes and debts that are not cost-effective,
whereas otherwise they would vote for that,
this education would be a positive externality and a public good.

Fred Foldvary