Out of the top 10 countries in this graph 8 were also amongst the first 10 countries to give females the right to vote. The length of time between these two occurances is around 100 years so it would be difficult to draw a direct link.
One could suggest that these countries still have a very progressive outlook on social issues such as equality and education.
An even more obscure link could be that females in these countries got a "head-start" on females of other countries by getting the vote so many years ago.

Traditionally literacy statistics have divided adults into two groups, those who can read and those who cannot. This division is misleading as the level of literacy of adults is really a continuum.

In this study, a low level of literacy represents a skill level lower than that required for successful completion of secondary education.

A person with low literacy may be able to read a little, but will have difficulty filling out forms, comparing data, integrating information and following complex or unclear instructions. Low literacy affects a persons' quality of employment, employment options, training opportunities, financial status, their ability to help their children prepare for school and their ability to access services.

In respect of the top 2, Australia and USA, rural firefighter numbers most likely impact significantly on this stat.
Both of these countries have a very serious rural fire problem. USA alone has well in excess of 1 million firefighters of which around 75% are volunteers according to
www.american-firefighter.com.
Australia has large numbers also, for example in the state of Victoria alone there in excess of 50000 rural firefighters,see www.cfa.gov.au.

In this study, moderate literacy is roughly equivalent to the skill level required for successful completion of secondary education.

Note that this statistic excludes people who function at a high level. See also Adults with at least moderate literacy

Class size indicates the number of students a classroom teacher is responsible for during the school year. Class size should not be confused with the more commonly used pupil-teacher ratio.

Pupil–teacher ratio is one method used to determine the level of resourcing in education. It is calculated from the number of students in a district compared with the number of EFT (effective full time) educators. The number of educators includes teachers with other responsibilities such as school management, pastoral care special education and counseling. For this reason the pupil – teacher ratio is typically lower than the actual number of students in an average class.

To gain a better overview of educational resourcing, other methods including expenditure per pupil and proportion of GDP devoted to public education should also be consulted.