if my child came out barely being able to understand very basic english and maths by year 5... thats a problem
I absolutley agree with you, if I knew my child was capable of achieving better results and wasn't I would be into the school quicker than lightening demanding to know what was going on.
However, just because a school rates badly doesnt mean that all the students are failing, it just means that have a higher percentage of students than other schools sitting below the national standard.
There are various reasons for this- and I am not making excuses here for all the schools out there, however, from my experience though the schools that rank poorly do have reasons- the school I am at at the moment has a large number of students who have English as a second Language, we have a large transisent popluation (up to 25% turnover through the year), we are in a low socio- economic area, with high levels of unemployment, single parent families etc- for some children they are more concerned where there next meal will be coming from, or more concerned about trying to find shoes or a jumper to wear to school, or getting home and cooking dinner and looking after younger siblings because mum works 12 hours a day to make ends meet.
Having said that though, we also have students in all year levels sitting in the top bands, and we run extension programs for these students, we run focused literacy programs to help improve the literacy levels of students who are more than 2 years behind- which means we have great programs available for students who are struggling.

However, to look up my school on the website you would know non of that- there is no facilities available to communicate this information. Coupled with the fact that schools across australia are compared, when students in WA schools are up to 12 months younger than students in the eastern states because in WA they start year 1 between 5.5-6.5.

Just my take on it, not saying it doesnt have it place, and the NAPLAN results have been available for schools (at least in WA) for ages on the internet, you just have to look up the school on the Department site- so I dont have a problem with this imformation being available, I just have issues with how it is being used.