Is the prayer of greeting the mosque obligatory upon entering a school mosque in which prayer is rarely performed?

The agreed-upon Hadith: "When one of you enters the mosque, let him pray two rak'ahs before he sits down" indicates that the mosque, defined by the definite article "al-" (the), implies generality. Thus, it includes every place designated as a mosque for prayer, and whoever enters it must perform the salutation of the mosque (tahiyyat al-masjid) in obedience to the command of the Prophet, peace and blessings be upon him.