Cutting kids off from social media is all about cutting them off from outside information and support. We desperately need a bill of rights for kids, it's tragic how many people are fine with treating them like property.
Many abusive parents already control all of their kids' time outside of school, and for some, the only place to find understanding & support is in forums like r/raisedbynarcissists or LGBT spaces.
Like adults, kids are informed by social media, and if we want to improve their mental health we need to actually address the problems they learn about there, instead of simply preventing them from learning about the real world.
Things like our unwavering march toward an unlivable climate, the malign growth of oppressive, theocratic, authoritarian movements in many governments around the world, the crushing inequitable grind of capitalist culture, or just the ignorant / abusive / bigoted mindset of many fellow citizens are all bad for anyone's mental health, but they need to be understood accurately to be addressed.