the science says we need to get R below 1
It's not saying R needs to be zero. Just below 1. That means that we don't have to cease all social contact, just some. Enough.
And the science will give some indication as to the types of actions that can lead to R less than 1.
Generally reducing social interactions. That reduction can be achieved in many ways. Say you normally see 2 people, and the science says that needs to be cut to 1. The science won't tell you which person to cut, just that you need to go from 2 to 1. The choice is yours not the science.
It's up to the politicians to choose the set of actions that they think will be best for society as a whole whilst achieving the R less than 1.
So scientist say we need to start closing off some social contact, but it's the politicians that have decided that if it's a choice between schools, pubs and household mixing, then schools stay open.
Science doesn't choose to keep schools open, it just says, if you close enough other things then schools can stay open and R will be below 1. Not 0. Some transmission will occur, some within schools , but at a low enough level that R slips below 1