Believe the scientists who told him that having schools open was massively spreading the virus. Look at the increase in the numbers since they went back in September. Listen to teachers who work in inadequate size classes for the number of children they have to teach.
In my school (i'm not a teacher) we had to do a RA to determine how many people should be in a class. With distancing guidelines we had a range in our classrooms of 4 people (that's kids and the teacher) up to around 7 or 8 in the larger classes. Spilling over into our hall we were even only getting up to numbers of about 25 max (it's not a full size senior school hall). Luckily we are a small special needs school and there are only 12-15 kids in a class so when everyone had to come back we only exceeded the guidelines by double. It must be ridiculous in mainstream with 30 kids in a class.
We've spent many thousands extra (we don't have the money) on PPE, cleaning products etc, we've implemented key stage bubbles, class bubbles, one way systems, being outside for lessons for periods. The kids and staff are still too close because the rooms aren't big enough. This doesn't include times when distancing must be broken or broken on purpose during physical interventions, kids spitting in the faces of teachers, staff having to deal with students who need toileting help, kids who have bloody noses, kids who need medication administered....the list goes on.
Again, it's impossible for the virus not to spread in schools. Yes kids may not get ill themselves, but they pass it on to relatives who then do get ill. The NHS is now close to being overrun and school being open is one of the main reasons.