Herd Immunity?

I must admit to be broadly of the same view as the Harvard Epidemiologist when I heard about the UK plan to attempt to establish 'herd immunity' for the Covid-19 outbreak (https://www.theguardian.com/commentisfree/2020/mar/15/epidemiologist-britain-herd-immunity-coronavirus-covid-19). 'Herd immunity' is a concept used in vaccination programmes to specify a minimum uptake rate that offers general protection to the population (it's of concern when MMR vaccination rates fall below a particular percentage). There is no vaccine for Covid-19 (and one is not imminent) so you would only get a partial 'herd immunity' by between 60-70% of the population actually getting the disease. There would certainly be some deaths, even if the more susceptible 70+ folk were all successfully isolated away for several months (and that's not going to be easy). I also don't understand the reluctance to close schools. Children may not generally show a morbidity rate anything like that in older folk but they do mingle with their relatives and would be likely to pass the infection on to members of their family. In fact, it is more than likely that the virus can be passed from human to human by anyone who has not yet developed symptoms (so, I don't understand the decision to cut back on testing for suspected contacts). But, then, I am only a simple Biologist.