There are two species of soy** that are used as food crops: Glycine max (common "soybean") and Glycine soja ("wild soybean"). According to the NCBI taxonomy browser (which plays fast and loose with its taxonomy), the lineage of SOY! is...
Superkingdom Eukaryota (eukaryotes)
Kingdom Viridiplantae (green plants)
Charophyta/Embryophyta group

Phylum Embryophyta (higher plants)
Tracheophyta (vascular plants)
Spermatophyta (seed plants)
Magnoliophyta (flowering plants aka. angiospermae)

Subclass Rosidae
Order Fabales
Family Fabaceae
Subfamilty Papilionoideae
Genus Glycine

**aka. soya, soja, soybean, soyabean, sojabean

Note the total lack of any class in the proletari...I mean, ::lineage above::. There is no One True Taxonomy eg. in some classifications, the flowering plants constitute a class (Angiospermae) and in others a division (Magnoliophyta or Anthophyta).