Many students of Sparta in high schools focus exclusively on written sources, particularly Plutarch. Aside from the fact that most written sources on Sparta have historiographical problems, it is also not balanced, since there are archaeological sources as well.
This powerpoint will take you through the archaeological sources on Sparta, most of which were found at the Sanctuary of Artemis Orthia.
My advice is where possible, focus first on archaeological sources, then the limited “primary” sources, then the “secondary sources”. (I’m inclined to call Plutarch and Aristotle ‘fourth-hand’ sources.)