The father of a private primary school pupil, who was prevented from writing exams because of unpaid school fees, has challenged the constitutionality of this policy.
On his side are two Durban-based advocates, appointed to represent the boy who was aged 10 and in Grade five at the time, who say the effect of the policy is "calculated simply to pressure parents" and punish the child.
"Independent schools can sue parents for fees, rather than victimise and humiliate learners," advocates Laurence Broster SC and Camilla Du Toit said in their written argument handed in to court.
While other courts have acknowledged the "contractual rights" of private schools and ruled that pupils can be excluded for non-payment of fees, the matter before Judge Mokgere Masipa in the KwaZulu-Natal High Court in Durban is believed to be the first to focus on the rights of the affected children.
If Judge Masipa rules in favour of the father - a teacher at a government high school who cannot be named to protect the identity of his son - it will affect all 760 private schools in South Africa.
When the matter was set down for argument recently, lawyers acting for John Wesley Primary School in Pinetown argued that it was "moot", because the fees had eventually been paid and the child had written the exams a few weeks later.
Evidence was that the family had short-term financial problems at the time and were in arrears of about R3 800. Their offer to pay off what they owed in installments was rejected by the school.
After the boy was excluded from writing exams in May 2016 - and forced to sit by himself in the art centre - they cashed in a funeral policy and settled what they owed.
But the dad, who represented himself, insisted that he wanted the matter heard "on an issue of principle".
The judge asked that the advocates come on board as "friends of the court" to represent the child.
At the heart of the application, they say, is the best interests of the child, and "his parents' trauma at not being able to pay his school fees on time should not under any circumstances be visited on him".
"The conduct of the school, on its own version, influenced by Independent Schools Association of South Africa (Isasa), was appalling and it cannot pass constitutional muster."
They labelled the Isasa's policy as "breathtakingly offensive".
The advocates said the fact that the policy affected so many schools, and about 160 000 pupils, was reason for the matter to be properly ventilated and, if necessary, curtailed.
"Judging from the jurisprudence thus far on the difference between public and independent schools, the effect of the contractual arrangements between the school and the parent have not been properly examined. Only the interests of the school, and not the child, are taken into account.
"Isolating the child in the art room while he should be writing an exam is not only victimising, but also extremely humiliating. His co-learners would be curious to know why he did not write the exam... confessing that his parents had not paid the fees must be excruciatingly humiliating.
"In this case, the child had done absolutely nothing wrong. He was a well behaved diligent learner."
'No one is obliged to remain at a private school'
In his written argument, advocate Warren Shapiro, for the school, questioned how a private school, whose sole source of income is school fees, could be expected to educate "on risk", and wait for a litigation process to unfold.
"This ignores that the parents elected to have the child educated as a private school and undertook contractually to pay the fees, and accepted the consequences of failure to do so.
"If this court finds those contractual limitations are unconstitutional, the court removes a significant and recognised difference between private schools and public schools.
"To add to this, is the consequence of an inability of the school to fund its operations, which is prejudicial to all of its learners and staff.
"No one is obliged to remain at a private school."
He questioned what rights of the child had actually infringed and what harm had been caused.
"There is nothing on the papers to suggest that the temporary exclusion was anything but that. It was no more than a proportionate means of securing payments for amounts agreed to be due."
Arguing that the issue remained moot, he said the court should not be determining "these weighty issues" when there was no need to do so.
Judgment has been reserved.