Secondary school students and their teachers will have to wear a face covering when schools return in September.
Education Minister Norma Foley has issued updated guidelines, saying the new rule will apply in cases where the two metre social distancing rule cannot be adhered to.
It is now recommended that teachers and secondary school students wear face coverings, similar to those worn in shops or on public transport.
While €102m in funding has been issued to primary and secondary schools to carry out minor works.
Guidance has also been circulated to schools, detailing how they can best access PPE and hand sanitiser supplies.
The minister said all recommendations published in the public health advice at the beginning of July - including physical distancing guidelines - still apply in all schools.
There has been widespread welcome of the updated advice from teachers unions.
ASTI General-Secretary Kieran Christie said: "Schools are working hard to implement the necessary safety arrangements in time for re-opening.
"Keeping schools open must be the priority, and this means minimising the risk of transmission within classrooms and other learning environments."
The Teachers' Union of Ireland (TUI) said it welcomes the updated guidance.
TUI President Martin Marjoram said: "The union has consistently called for publication of this guidance as early as possible so that schools can plan accordingly and procure the required equipment.
"It is now vital that the required resources are provided to schools to ensure that this crucial protective measure is in place when schools re-open.
"The health and safety of students, staff, their families and communities must remain the key concern for all and the TUI, therefore, will continue to address any arising issues with the Department ahead of the re-opening of schools."
INTO General-Secretary John Boyle added: "INTO wrote to the Minister for Education earlier this week requesting an urgent review of face coverings in the primary sector.
"We welcome today's announcement from the Department of Education that teachers who are unable to maintain two metres social distancing in their classrooms are advised to wear face masks or visors as appropriate.
"Schools will have the option of ordering face coverings centrally on the newly established government procurement portal."
The Department of Education has also brought forward to August the payment of the annual minor works grant to primary schools.
This is worth approximately €30m.
And an enhanced minor work grant, which matches the 2019 payment, has also been issued directly to schools.
Funding of €40m has also been made available for additional supervision at secondary level.
Of this, €12.3m has already been paid to schools for the first term - with the balance payable in 2021.
Measures to increase the supply of teachers at both primary and secondary level are also being adopted.
This includes offering additional hours to 2,800 teachers who are working part-time, allowing job-sharing teachers to work additional hours and making it more attractive for teachers on career break to provide substitution and supervision cover.
