They somewhat reduce it. Perhaps by 50%, against currently dominant variant (which is itself of course subject to change.)

Everything that helps to reduce prevalence helps kids stay in the classroom.

Here in the UK there's a huge subpandemic among 5-11 year old schoolchildren, a group which are not vaccinated. I have a child of this age, off twice with covid in the last few months. I wonder if it'd be more effective to vaccinate them or to just do away with self isolation rules for them. The problem is the spillover into parents, who will be at higher risk due to age and possobly at much higher risk if clinically vulnerable.

On this one I find it hard to form a strong opinion.