This source suggests traffic is prohibited between 8:00 and 8:50 am.  But it may be outdated + one would expect it to be closed in the afternoon too.
https://bx1.be/jette/jette-possede-desormais-la-plus-grande-rue-scolaire-de-bruxelles/

In that case, it might be tagged like this:
motor_vehicle:conditional=no @ (Mo-Fr 08:00-08:50)