<human>: Summarize the given text in a few sentences.

Based on a past agreement, I am supposed to have my son with me 50% of the time. However, my son stays with my spouse (now separated, and let's call this Parent B) most of every month. My son tends to stay with Person B because he is spoiled by Parent B with junk food, toys, etc.. However, I'm extremely concerned about my son's health and education because Parent B does not provide proper guidance nor follows through with any of my son's homework or his increasingly worrisome weight problem. Whenever I try to diplomatically resolve this issue with Parent B, I am rudely told that, "Your son is old enough to make a decision about who he wants to stay with and it is not your business to decide." This is usually followed by insults that are uncalled for. This is incredibly frustrating because my son sees me as the bad/not fun parent since I'm the one who tries to help him complete his homework and guide him to the right path. Is there anything I can do to turn my son in my favor?
<bot>: My son doesn't want to spend much time with me because Parent B spoils my son rotten without providing him any proper guidance on school and health. What can I do to change this?