It's reassuring to see the majority agree but there's a significantly worrying amount who don't.
So far, we have about 100 responses to this post and a vast array of views on what school rules should be followed and what school rules shouldn't. Take a school with 1,000 students and (for the sake of argument) two parents each. That's 2,000 adults all with an opinion as to how the school should be run, the majority of whom won't be professionals in that field or work in that school. How on earth can a school legislate to keep everyone happy? Explaining and justifying the reasoning behind (what some parents deem to be) "ridiculous" rules would be an absolute waste of resources.
If you don't like the rules, find another school. If the rule is so "petty" (some people have mentioned sock colour in that vain) just follow it - what harm does following it do? It's absolutely ridiculous for parents to push back against such trivial matters and they do their children absolutely zero favours introducing the idea that observance of school rules is at the parent's / child's discretion. Where does it end?
Too many parents forget that teachers are professionals. In what other profession do people believe they have the right / knowledge to question the professionals to the extent people do with teachers? Take a look at the general behaviour in public, private and grammar schools. It is (generally) much better than in comprehensive schools. Those students follow the school rules and, yet, they are also taught how to properly and effectively challenge ideologies and the law.
Parents should also remember that children are just that - children. They are learning about the world. They are definitely not qualified to decide which rules in a school are good rules and which rules are bad rules - the vast majority have not yet developed the skill properly (if you've done plenty of reading on brain development in teenagers, you'll understand), nor have they gained the education or experience to have any idea about how to run a school. When a parent invites the idea that some school rules aren't worth following, they open their children up to the idea that the rules are flexible and at the whim of the individual. Which just isn't true. As with the law, we cannot, as individuals, decide which laws we think are worth following and which are not.
Once a child has it in their mind that rules are discretionary, then you've undermined the entire educational establishment and, sadly, one of the consequences is that when a child finds a rule they don't like or it's a bit more difficult to adhere to, they simply won't follow it.
Teaching children to challenge things is absolutely not teaching them that some school rules are stupid (or so they / their parents think) and therefore they don't need to be followed - that just gives them the idea that they know more than professional adults, which they quite simply don't. Teaching children how to bring a challenge is far more sophisticated and, whilst your child is moaning about being punished for not coming to lessons properly equipped, every other Tom, Dick and Harriet who has already learned about taking responsibility for oneself (and arrived with the correct pens, books, uniform etc) is learning how to properly change the world.