Albert Barnes Commentary 1 Kings 12:31

"And he made houses of high places, and made priests from among all the people, that were not of the sons of Levi." — 1 Kings 12:31 (ASV)

He made a house of high places — that is, he built a temple, or sanctuary, in each of the two cities where the calves were set up. The writer uses the expression "house of high places" contemptuously, implying that the buildings were not real temples, or houses of God, like the one in Jerusalem. Instead, they were merely on par with the temples on high places that had long existed in various parts of the land.

Made priests of the lowest of the people — This is more accurately translated as priests "from all ranks of the people." The fact that the Levites did not accept Jeroboam’s innovations and transfer their services to his two sanctuaries must have been a consequence of their faithful attachment to the true worship of Yahweh. In all probability, Jeroboam confiscated the Levitical lands within his dominions for the benefit of the new priestly order (2 Chronicles 11:13–14).