Is Serpent of the Pass legal in Standard, Modern, and Commander?

Serpent of the Pass is legal in: Standard, Modern, Pioneer, Legacy, Vintage, Commander, Historic.

Serpent of the Pass

Q: What type of card is Serpent of the Pass?

Serpent of the Pass is a Creature — Serpent. Its oracle text reads: "If there are three or more Lesson cards in your graveyard, you may cast this spell as though it had flash. This spell costs {1} less to cast for each noncreature, nonland card in your graveyard."