If you want to use the definition of a main road being one that goes directly from one town to another that’s fine. In the US that’s called a highway.
No matter what you call it, the larger road that goes near a school is the same in Germany and the US. Both have two way traffic.
And no there’s no speed bumps why would there if the road is narrow enough and people naturally drive slow enough, there’s no through traffic, the residents don’t race on it, etc.
Given that it is residential that connects to two other roads, it has through traffic. It would need to be a dead end to not have through traffic. The road isn’t so narrow that busses can’t pass each other. It’s why I linked one school that has a labeled public bus stop.