Secondary school teachers have been urged not to conduct online "live-streamed" lessons during the coronavirus outbreak.
Guidance published this morning from the NEU teaching union states: "Teachers should not live-stream lessons from their homes, nor engage in any video-calling, unless in exceptional circumstances with the parent".
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And in separate guidance for primary staff, the union said: "Online lessons are not desirable for primary children as the teacher-pupil interaction is not easily replicated."
"Many children need a lot of guidance when working and cannot be left for long periods of time to complete complex tasks".
The union said tasks set by schools should ideally be accessible for pupils without internet access.
Its guidance states: "Any contact between pupils and teachers should only be through a platform provided by the school and not through personalised accounts open to public viewing, comments or sharing.
"The NEU advises staff not to use or exchange personal email addresses or phone numbers with pupils."
"No teacher should be expected to carry out any online teaching with which they feel uncomfortable or in the absence of agreed protocols."
Nansi Ellis, assistant general secretary of the NEU union, said they have "a lot of different concerns", including around teachers' online safety.
It is "easy" to misuse this type of video content, she said, adding: "We don't want to put our members in any position where they could end up having their image shared. That's a concern for us."
She said that, for example, screen grabs could be taken of a teacher, then posted on other sites.
There are also issues with access, Ms Ellis added. It could be "completely impossible" for both teachers and pupils, she suggested, with other siblings and parents working from home and internet access all likely to be factors that could cause difficulty.
Ms Ellis also said that some children "won't have internet at all", adding: "If you've got parents working from home or other siblings, you might not have enough kit for everyone to join in."
Children could listen in to the lesson at a different time, but this may also be stressful for them if they feel they are missing out.
She added: "We are concerned about workload and how much you can be expected to do, as a teacher, of this sort of thing."