My own belief Lizzie (avoiding judgementally loaded words like 'correct') is based on the considerable evidence that mobile phones, particularly those with cameras, have been used extensively in bullying and that the head teacher - presumably in consultation with the school governors - should have the authority to ban mobile phones during school time if he/she believes it could also prevent or diminish other specific problems such as theft etc

Furthermore my personal view is that is also incumbent upon parents to familiarize themselves with the rules of their child's school as parents and teachers need to work together to promote the safety of the pupils.

As you have pointed out, if you believe schools should have no rules and exist in some state of happy anarchy then the option of home teaching is available to you.
Again, entirely personally, I also believe that the absence or non-recognition of order is not a good foundation for working life

I have answered your question; may I in return ask if you believe children should be allowed to bring anything they want into their school?