The government has updated it guidance on which employees can be put on furlough to include those caring for children at home:
If your employee’s health has been affected by coronavirus (COVID-19) or any other conditions
Your employee is eligible for the grant and can be furloughed, if they are unable to work, including from home or working reduced hours because they:
are clinically extremely vulnerable, or at the highest risk of severe illness from coronavirus and following public health guidance
have caring responsibilities resulting from coronavirus (COVID-19), such as caring for children who are at home as a result of school and childcare facilities closing, or caring for a vulnerable individual in their household