Schools must "only use domestic social networks" for their communication, the ministry said in a statement, according to the reformist-linked news agency.
Telegram is the most popular social network in Iran. In 2017, the app claimed it had 40-million monthly users in the Islamic Republic.
Instagram is also very popular, and companies in Iran -- like elsewhere -- often use both platforms to communicate directly with customers.
Less used, Facebook and Twitter are blocked in Iran, but easily accessible using a virtual private network (VPN.
During a wave of protests that hit dozens of Iranian cities over at the start of the year, Iranian authorities temporarily banned Telegram, accusing the app of allowing foreign-based "counter-revolutionary" groups to fuel unrest.