Muslims finally trying to align themselves with Christian values and it's somehow painted as a negative. SMH

Child protective services exist, laws exist, children with once thought eradicated illnesses exist. Why? Because parents are terrible at their fucking jobs. Raising a child stops being their job when it's about a future member of society that will interact with other members of society. A child isn't a plaything for the parents. If a child was truly the property of their parents then post natal abortion would be legal, but it isn't.

So I thoroughly reject the notion that people can't tell parents how to raise their child. I mean the whole reason school even exists is because parents cannot educate them themselves.

The assumption you are making here is that things are black and white and that society has a right to dictate how a parent should raise a child because there are parents who do not know how to raise their kids (if such is the case, then shouldn't the parents be the one forcibly educated and not the kids?). Like I said, it is not about agreeing with what they are doing but sympathizing about where they are coming from.

There will always be things I will not agree on (for example, if schools started teaching "economics of oil and energy" in order to sell the idea of fossil fuel to kids, you can be sure I'll be outside protesting it) and I reserve the right to protest if such a thing occurred.

The issue of LGBTQ/gender isn't black and white (like physical abuse is) and it isn't an established science like medicine (that is why there is still some debate about gender up til this point, it is still relatively new and is not yet universally accepted as a scientific truth within most of society). There will always be people who disagree with it and there will always be people who feel that they know best WHEN to discuss these issue with their kids. As society goes, I feel this is very benign. You can teach kids all about the existence of LGBTQ in the world but if you do not teach them to not be miserable little shits I don't see how this will help them become better people in the end. Maybe start with teaching kids not to be bullies/miserable little shits first?

Hell, aren't parents not forced to vaccinate their kids in most countries (personally, I feel that this should be made mandatory first before anything else)?

Not everything taught in school is something we can agree on (there was a time when religion and prayer was an integral part of schooling in the US, for example). I feel I should have the right to opt out of things that do not have a directly attributable negative effect to society (unlike vaccination that can cause outbreaks if it is not done) or at the very least the school should have that conversation with the parents when the parents don't seem to have much of a choice here.

In the end, I don't agree with their protest but I sympathize with their situation.

If your not happy in a country where the rules are different why not return back to your own country. No one forcing you to stay here.

Because rules aren't always something you have to agree on (unless you're in a despotism, that is). You have to follow them, yes. But people are free to protest when they do not agree with what society is forcing them to do. That is how conversations happen, compromises are made or minds minds are changed.

People seem to forget the reasons why most countries have mandatory education systems. One of the reasons is actually to educate children independently of what their parents think. Turning children into good citizens has always been one of the major goals of elementary and secondary education.

In the UK it is apparently important to see LGBTQ people as normal humans in order to be a good citizen.

You can't force someone or "his children" to be what you want them to be 

Good thing this didn't happen here.

People can agree on the concept (educating children to be good citizens, teaching them to see the importance of LGBTQ issues) but disagree on the methods (teaching it to 5 year olds).

They teaching 5 year olds that some men love other men or that some kids have two moms. What is wrong with that? It's just a factual description of our reality.