The reason there is no school for the 144,000 is because the "Governing Body" successfully conducted a power grab much like Rutherford did of the Watchtower after the death of Russell.
If memory serves, the Watchtower taught for years that the "Faithful and Discreet Slave Class" was all the remaining member of Christ's heavenly kingdom government still on earth. This caused heart burn for the powers that wanted to be at Watchtower HQ. A campaign to silence those who professed to be of the Annointed was secretly carried out. My belief in this is because my father was one of many victims brought to my attention.
The newer doctrine taught by the Watchtower of the Governing Body solely being the Faithful and Discreet Slave turned a figuratively bloody coup into a figuratively bloodless coup. The Watchtower successfully cast doubt on all who profess to be of the Annointed and as a result the whole remnant of the 144,000 still on earth was reduced to a bunch of loons distanced from the rank & file. Mission accomplished Governing Body. 8 Banana Republic Generals smoking Cuban cigars with their high dollar scotch.