Baby rejects bm

Hi Mummies, what will you do if your bb rejects bm? My LO is 7mths plus and is on mixed feeding since ifc. Initially, he 8s ok with bm, but gradually, i was informed by the school that he prefer fm compare to bm. Currently, has started semi solids as well. What will you do if you have frozen bm in the fridge? Will you throw? Thxs,.