Parents have been urged to respect social distancing when collecting their children from school.
It follows complaints about gatherings at school gates not respecting the 2m rule put in place during the pandemic.
Powys council said it had received "a number of reports" from head teachers in the county.
Concerns were also raised about parents contacting the schools asking them to confirm whether or not members of staff had tested positive for coronavirus.
Phyl Davies, cabinet member for education, said: "We know that many youngsters have started primary and secondary school for this first time and parents and children are excited, but I would urge parents to be mindful of the coronavirus guidance and work with the council and the school to keep everyone safe.
"We have done a lot of work with school leaders to make sure that children are safe in their school and that the risk of the virus spreading is minimised.
"It would be a shame if this work was undone by parents and older relatives ignoring social distancing by gathering outside the school gates."
The council said it understood parents were anxious, but asking for information about whether individuals had tested positive for the virus was "inappropriate".
It said: "It would not be up to headteachers to inform parents about any potential coronavirus case within their school.
"This would be down to the Test, Trace, Protect programme which would trace the contacts of people who test positive to put a stop to the spread of coronavirus."