Why would you ban a relatively harmless religious custom? Wouldnt that infringe on peoples right of freedom of religion? And even if it has nothing to do with religion, if people decide its for the best of their kid (even if its based on nothing) then they should be able to do that right?
We let far more damaging things being done to kids, like parents not giving their kids shots against polio (turns you kid into an autistic kid) and instead rely on prayer or alternative bullshit medicine with all the real proven health risk consequences. Or not sending your kids to a school instead using homeschooling, denying your kids a whole lot of social experience needed to properly function in a modern world. Not to mention the fact that a lot of parents use this to teach their kids a whole lot bullshit because they arent qualified teachers or because they want to brainwash their kids into believing the same bullshit as they did.
So, there are far worse things you could and perhaps should ban first.