A teacher-purchased license is paid for directly by the teacher. It is a one-time purchase and the license is owned by the teacher. The materials can be used only by that teacher at whatever school the teacher moves to in the future.
A school-purchased license is purchased for each teacher with school funds. It is a one-time purchase and the license stays with the school. If the original teacher leaves the school, they may not take the materials with them. Their login will be reassigned to a teacher of the school's choosing.