A SIM card connects a device to a mobile network. A mobile network provides internet access — even on phones marketed as "basic" or "dumb." That means any phone with a SIM card in it has some level of internet connectivity, regardless of how simple the device looks on the outside.
If the goal is giving your child a phone with zero internet access, the most reliable way to achieve that is to remove the SIM entirely. No SIM means no mobile network connection. No mobile network means no mobile internet. The risk is not managed or filtered — it is eliminated at the hardware level.
