It depends on how heavy handed the approach is. A kid could learn about using a vpn or proxy service to bypass dns or dpi based content filtering but if you properly configure the parental controls on iOS or android there is pretty much nothing they are going to be able to do. If they are that determined, I think you need to have a conversation about making good choices themselves and trusting them not to consume harmful content.

I was able to bypass the content filters on the PCs when I was in high school because it was a shitty content filter that could be bypassed by killing the process in an unelevated task manager. My kids are going to have to be more resourceful than that