Re: Are historians such as Plutarch and Aristotle primary or secondary sources for Sp
The topic of Spartan Society in the NSW HSC syllabus covers roughly the 5th C. BCE (ie, the 400s) and down to Sparta's decline with the Battle of Leuctra vs Thebes in 371BCE.
Plutarch, as commented above, although an ANCIENT source is still a SECONDARY source because he was writing well after the time of classical Sparta and basing his work entirely on other sources (much like we do).
Aristotle can be both primary and secondary depending on when you study; for the HSC topic, Aristotle is largely secondary (only just) as he was writing in the 300sBCE.
Don't let that deter you though. Primary sources on Sparta are scarce, Plutarch and Aristotle did have had access to sources that have not survived for us today.
Don't forget Xenophon... also helpful ... though he was Athenian he lived in Sparta a bit and was fairly favourable towards Sparta (bias)
Also Thucydides comments on Sparta in the context of the Peloponnesian War.