Hundreds of thousands of families across England are waiting to hear whether their child has secured a place at their first choice of primary school.
School leaders said parents are likely to be feeling more anxious on what is known as National Offer Day due to the pandemic.
Paul Whiteman, general secretary of the school leaders' union NAHT, said Covid-19 will have prevented many families applying for September from visiting schools in person.
He said: "It is vital that no child going through the primary admissions process this year should be disadvantaged. Support must be in place for families to navigate what can be a daunting process.
"For those families not getting their first choice of school, the appeals process will be going ahead, albeit virtually. This process must be as robust as ever and be made clear to parents through effective communication and advocacy, where required."
Mr Whiteman added: "This can be an anxious time for families. Choosing the right school and securing a place there is a huge moment in a child's life. And of course, these feelings of anxiety will only be heightened by the unique circumstances caused by coronavirus.
"Schools have gone to great lengths to find innovative solutions so that parents can make informed choices, but the reality is that in many instances families could be applying for schools they simply haven't been able to visit in person."
England's school system has been under pressure due to a rise in the school-age population.
This has been fuelled by a spike in the birth rate in the early 2000s that has made its way through primary schools and is moving into secondary schools.
Official data shows that, last year, 90.2 per cent of pupils were offered their first choice of primary school - which was down slightly on 90.6 per cent in 2019.
Last year, the Department for Education (DfE) changed its rules amid the pandemic so that parents unhappy with their school place would not have to make an appeal in person.
The temporary change has been extended until the end of September 2021 due to coronavirus restrictions.
Appeal panel hearings will be able to take place "either in person, by telephone, video conference or through a paper-based appeal".
The Good Schools Guide has warned there could be delays to appeals processes amid the pandemic.
Advice on its website says: "It is also possible appeals deadlines are delayed to accommodate inevitable difficulties."
The guidance adds that appeals for reception places "can only occasionally be won on grounds other than technical, procedural grounds".
But it says: "The coronavirus school shutdown made clear how crucial a role parents can play in their children's education. It's worth remembering that especially in the early years of school, a parent's input will go a long way to cover for any deficiencies in the school.
"Reading with your child every night, keeping them supplied with books, taking them to stimulating places (if possible), chatting over the dinner table, encouraging their curiosity will all do a great deal to promote your child's learning."
Julie McCulloch, director of policy at the Association of School and College Leaders (ASCL), said: "Hopefully the majority of parents will be successful in getting the place they want and can look forward to settling their children in to the school of their choice come September.
"However, this annual process highlights the way in which our education system pits one school against another, often using narrow measures which reflect the neighbourhood in which a school is situated rather than any inherent difference in quality.
"The means that some schools become highly sought-after, while others suffer from falling numbers of pupils.
"This leads to a vicious circle in which struggling schools receive less funding and struggle to attract teaching staff of the high calibre they need."
Ms McCulloch called on the government to urgently address the issue through an accountability system which focuses on supporting schools in more challenging circumstances, as well as "sufficient funding to ensure that every child has access to a good school, right on their own doorstep".
Additional reporting by PA
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