All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
Islam has prohibited eating up orphans property unjustly since Allah, The Almighty, Said (What means): "Those who unjustly eat up the property of orphans, eat up a Fire into their own bodies: They will soon be enduring a Blazing Fire!" {An-Nisa`/10}. Muslim scholars have regarded such an act as one of the grave sins as it reflects injustice and betrayal of trust.
Moreover, if the school and the medical centre were established from the money of the orphans or the donations made to them then it is unlawful for the society to donate their income or spend it in favor of other parties since the profits of the school and the medical centre emanate from the orphans` money. Therefore, it should be spent on them. In addition, if the internal regulations address the orphans in particular then they must be adhered to.
As for matters that indirectly benefit the orphans, they are for their own good, eventually, and all of this can be figured out by reviewing the internal regulations of the society and its objectives. However, if the school and the medical centre were established from donations other than those made to the orphans then there is no harm that the society dispose of the revenues of these facilities as it sees fit provided that donors were informed about that. And Allah Knows Best.