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)
Streptophyta
Charophyta/Embryophyta group
Phylum Embryophyta (higher plants)
Tracheophyta (vascular plants)
Euphyllophyta
Spermatophyta (seed plants)
Magnoliophyta (flowering plants aka. angiospermae)
eudicotyledons
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).