The latest macOS that can be installed on your MacBook Pro A1278 (Mid-2012) is macOS Big Sur. Model: MacBook Pro A1278 (Mid-2012). Processor: 2.5 GHz Core i5. Storage: 250 GB HDD. RAM: 8 GB (upgradable to 16 GB).
Lot of 4 Apple MacBook Pro A1278 & Macbook A1502 Laptops 13" LCD screen 4 Parts
Apple MacBook Pro A1278 13'' Mid 2012 (500GB HDD, 8GB RAM, Intel Core i5 3210M)
Apple MacBook Pro A1278 2011 13" 2.3GHz i5 4GB RAM 320GB HDD os10.13.6 794Cycles
Apple MacBook Pro A1278 13.3" Laptop - 750 GB, 2.8 GHz, Intel Core i7
MacBook Pro A1278, 4GB RAM, 1TB HDD, DVD, Works!
Apple MacBook Pro A1278 13.3'' Laptop (NO HDD / SSD)
