It does not necessarily have to be a roadblock. In my neighbourhood there is a t-junction along the water. A “schrikhek” prevents cyclists from driving into the water in the dark. It is therefore located next to the path and only serves as a warning sign.
The report of the “schoolstraat” does not suggest that the road will be physically blocked and I actually don’t see any relation with fences.
edit: I overlooked the part “waar tijdelijk en tijdens bepaalde uren aan de toegangen een verplaatsbare afsluiting geplaatst is” (where temporarily and during certain hours a removable blockade will be placed at the entrances).
In the pictures in the first comment it is unclear why those fences are located there. Do they block any access to the road area behind it, separate traffic flows from each other or signal a dangerous situation? These fences should have a common feature because otherwise there is no reason to introduce a new tag for them.