Parents will not have to return their children to French schools when classes resume beginning May 11, when officials hope to start easing the coronavirus lockdown in place since mid-March, the presidency said Thursday.

In a meeting with mayors from across France, President Emmanuel Macron said any lifting of the confinement rules would be adapted to each area, based on how hard the Covid-19 outbreak had hit, his office said.

The youngest students and those at greatest risk of falling behind after weeks of home schooling will be the first to return to classrooms, but "without any obligation" for parents worried about exposing children to infection, it said.

Other students will begin returning in the following weeks, though Education Minister Jean-Michel Blanquer has said class sizes will be limited to 15 students - prompting questions about whether schools would be able to adapt and open back up for everyone.

It also remains unclear whether teachers or students, along with the general public, will be required to wear masks in order to prevent a new surge in coronavirus cases as the stay-at-home orders are gradually lifted.

Macron told the mayors that for now masks will only be "recommended," since surgical masks and the more protective FFP2 or N95 filtering masks, already in short supply, will be reserved for health workers.

Instead, people will be urged to wear homemade or non-medical grade masks, which are likely to be required when using public transport, Macron's office said.

The government official in charge of lifting the lockdown, Jean Castex, is expected to present details on the plan in early May.

More than 21 000 people have died in France from Covid-19 so far, and despite signs that the spread of the virus is slowing, hospitals remain under serious strain.

The government has already said that even if restrictions are eased on May 11, restaurants, cafes and cinemas will remain closed and large public gatherings such as concerts and sporting events prohibited.