Document compliance with the required STC rating for adjacent spaces, with specifics depending on your compliance method:

If doing STC rating calculations based on ANSI standard S12.60-2002 section D2.4, projects will need to fill out the LEED Online credit form including adjacent space type and STC of assembly for walls, floors and ceilings of all classrooms and core learning spaces. 
If doing STC rating measurements based on ANSI standard S12.60-2002 section E5.1, projects will need to fill out the table on the LEED Online credit form including adjacent space type and STC of assembly for walls, floors and ceilings of all classrooms and core learning spaces. Projects must also provide a narrative describing the methodologies used to conduct the STC measurements and verify that they are in compliance with section E5.1 of the ANSI standard.