Roads are typically 2 lanes one in each direction. You already know this because you said a solution would be to remove the lane marker.
I’m someone else.
So you have a road with an elementary school, and 2 miles further down is a middle school. Even without that you have buses passing each other during pickup because busses only pickup kids on one side of the street so you don’t have young kids crossing roads.
Lots of questions here: Why can’t kids walk 500m to the next bus stop? Why are streets so unsafe so that kids can’t cross them?
Why assume that there’s no larger road in between those smaller roads? Roads generally form a hierarchy, you have big ones feeding into middle ones feeding into small ones. Small ones should absolutely be safe to cross, also without explicit crossings, because they’re traffic calmed and don’t have much traffic in the first place. That’s where houses and schools are, where there’s no through-traffic because even if they aren’t cul de sacs who would drive through a road you can’t drive fast on when there’s a mid-level road that you could take.
What do you call a section of inner city bounded on all sides by a road in your country?
Straßenblock. Let me put it differently: We don’t have grids and nothing is regular. This is about as grid-y as it gets and if you zoom in you’ll notice that the interior streets have no lane markers and some even are cobbled. Those connect to a street ( south, Hallerstraße) with bike lanes (don’t need those on smaller streets because there’s not enough traffic to warrant them), which connects to a four-lane (plus bus lane) street, Grindelalle, west. The intersection looks a bit crazy but it’s actually safe for pedestrians and you should’ve learned how to cross streets safely and what traffic lights are in Kindergarten. You’ve also been there with your parents (going shopping or whatever) a lot of times, nothing scary really. That kind of density and housing is probably illegal to build where you are (it’s illegal pretty much everywhere in the US and Canada).
And mind you Hamburg is awful when it comes to urbanism, way too car-centric. Not because of lack of public transport but because politicians are unwilling to kill off car traffic and the whole city is full of rich fucks with too much disposable income.