Albert Barnes Commentary 2 Kings 2:7

"And fifty men of the sons of the prophets went, and stood over against them afar off: and they two stood by the Jordan." — 2 Kings 2:7 (ASV)

Fifty men of the sons of the prophets - We see from this how large the prophetic schools were. It is implied that the “fifty” were only a portion of the school of Jericho. They ascended the abrupt heights behind the town, from where they could see the entire course of the river and the opposite bank for many miles.