I believe the expectation is for the teachers to give children who are in school, time to complete the work that has been set for all children and to provide support where necessary, similar to those at studying at home.
If the teachers taught in school that would not be fair on the children who do not have access to school and put them at a disadvantage.
In many cases (including mine), children at home are not getting quality, on tap support/teaching from parents as they too are trying to work from home, mine are largely having to be left to their own devices.
What teachers are doing: setting work for all children to do remotely or in a class setting, making calls to vulnerable children/social services, planning for next term, keeping up with training, having staff meetings, answering emails/twitter feeds, marking work submitted online, supporting their own children at home, coming up with creative ideas to entertain children who after in school for extended hours etc etc.
Our headteacher and teachers I know say they are working harder than ever.
None of this is ideal or perfect, but everyone is doing what they can to make the best of a bad situation.