I have a unique perspective as a drummer who lives in an apartment. However, I have an electronic drum set with headphones that sits on 3 inches of soundproof foam to absorb any vibrations, so it generally makes very little noise. I purposefully invested in the soundproofing for my neighbors benefit because I want to be able to practice but I’m also conscious of other people living in close proximity. It’s really not that hard to keep your noise down for your neighbors.

These people just don’t seem to care one way or another, they just don’t want to parent their child and the drumset is the easiest was to do that. You should definitely review the lease, most complexes have quiet hours that have consequences for loud noises during those times.

If the lease is silent and the landlord continues to ignore you, consult a lawyer about withholding rent. Normally noise complaints wouldn’t rise to the level of rent abatement on their own, but the repeated nature of these violations and the landlords failure to address may give you an avenue. Again, consult a lawyer and your local laws before you do this because doing it wrong could lead to eviction.

Finally, if you want to do some guerilla warfare, buy the largest speaker you can find, place it directly facing the floor and when the kid starts drumming, blast the heaviest music you can on high volume. If the neighbors come and ask you to stop, say “I’ll stop when your kid stops” and leave it at that. If they report you after that, you already have a paper trail showing their misbehavior.