"It recedes after two-three hours, but it happens twice a day for a few days, so no classes are possible. Children only come for the midday meal," a teacher at the school said.
There are complex and multiple causes behind sea water invading lands in this vast deltaic ecosystem, and the submergence of islands such as Lohachara and Suparibhanga.
Sea water invades the classrooms to a height of one-and-a-half feet
The landmass itself is subsiding at four millimetres a year. There's erosion caused by river flows. Structures built by the Haldia port authorities have accentuated erosion many kilometres downstream, in Ghoramara and some parts of Sagar Island.
Having said all that, there's no doubt that the finger of global warming is beginning to press harder. Studies suggest that relative sea level rise, which was little over 3mm a year between 1985 and 2000, increased during the first decade of this century, land subsidence included, to a staggering 12mm a year.
The combined effects of these factors, human and natural, has meant for tens of thousands, the abandonment of agricultural land and homes to the sea, and forced migration. All along the coast in G-Plot, Sagar, Ghoramara and other islands of the Sunderbans, innumerable families are being forced to set up home elsewhere.
It is an ongoing process as people leave for more inland parts of Sagar Island or migrate to join the labouring poor in Kolkata, and as far as Kerala to do construction work. Others prefer to stay and change occupations to fishing so as to avoid having to migrate. Many farmers end up as agricultural labourers.
Sunderbans confirms one of the tragic ironies of global warming: those least responsible for it end up as its greatest victims.
Those that remain fight a grim battle against the invading sea - in one house we stayed at one edge of Sagar, packed sandbags were piled up to one side of the door, used as a barricade when the tide comes in during certain months.
Their lands in front of the house had turned saline, the freshwater body rendered useless; all along that stretch of coast were abandoned homes and lands, broken trunks of dead coconut trees jutting into the sky creating a landscape one can only describe as surreal.
What's happening as a consequence of all this is a continued fragmentation of families and of communities.
A couple of things differentiate the displacement happening here in the Sunderbans from displacement elsewhere in India: one, the number of times that people have been forced to shift. We met one old couple that have moved eight times so far. Three to four moves inwards are commonplace. And unlike earlier years, it's getting more difficult for people to find new land to till.
The second and crucial difference is a vastly reduced agency. Displacement from industrial and mining projects elsewhere catalyses local people coming together and resisting the process. In the case of displacement in the Sunderbans due to sea level ingress, such collective agency is largely absent. It is at best restricted to a form of climate adaptation to buy time.
A repeated refrain across different islands was the demand for embankment, for higher embankment, for sturdier embankment made of boulders and concrete. One political party's poster in G-Plot in Patherprotima Block reflected this pent-up demand: "If you want a higher embankment," it went, "vote for us". How one can build resilient embankment and still allow for drainage and thereby avoid internal flooding is moot.
Much as land subsidence has been a weightier factor here historically, that won't be the case for long. The IPCC's latest Summary for Policymakers said that sea level rise in this century could be as much as a metre. Subsequently, a group of 90 scientists from 18 countries who research sea level rise said it would be even higher.
Eminent climate scientist James Hansen has been writing for years that 21st century sea level rise will occur at an accelerating pace due to a non-linear melting of the great ice sheets on Antarctica and Greenland. We are talking about sea level rise this century that would be anywhere between 5 to 15 times the rise we've had thus far.
What's deeply worrying - or ought to be, at any rate - is that what we are seeing today in the Sunderbans are glimpses of India's future. Sea level rise in much of India's 7,500-km coastline would very likely be as much as Sunderbans' present 30 years from now.
Kids all along India's coast may be delighted that their schools have unscheduled holidays, but we are facing coastal erosion, the destruction of agricultural lands, salinity in groundwater bodies, storm surges, forced migration, and potential conflict, on a scale too horrifying to contemplate.