I am familiar with the use of "shift" with respect to certain occupations, but not with respect to schools. Maybe you meant this? He changed the class schedule from morning to afternoon.
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Mr. TomHe changed his school from (the?) morning shift to (the?) afternoon shift.So here you're saying that the school that he owned and operated went from being open for business in the morning to being open for business in the afternoon. Is that what you meant?