The government cannot say how many Covid cases in England are being prevented by sending pupils home from school to self-isolate.
The BBC has been told it does not monitor how many children self-isolating end up getting the virus.
It means the effectiveness of the policy cannot be fully judged.
Some 279,000 children are currently being asked to isolate at home because they have had close contact with an infected person in school.
That equates to 20 pupils being asked to self-isolate for every one confirmed case.
This is despite research suggesting children, particularly younger children, are less likely to transmit the virus if infected.
Ministers have indicated they want to see the system, which requires 10-day self-isolation after being classed as a close contact, replaced by the start of the new school year, after the summer.
And they are conducting a trial to see if rapid testing of close contacts can be used instead of self-isolation.
But they said the policy, introduced in September, had played a “vital” role in helping break the links in transmission.
However, Prof Robert Dingwall, of Nottingham Trent University, said the lack of data on who was testing positive during self-isolation meant it was unclear what benefit the huge disruption to education had even had in terms of controlling the virus.
And given most adults had been vaccinated and children remained at very low risk, there was no reason to even introduce testing in the autumn as a replacement for automatic self-isolation.
“I don’t see why we can’t get back to normal in September and children stay at home if they are sick,” Prof Dingwall said.
“There is growing levels of natural immunity building up in children anyway and we know schools are not big drivers of transmission.”
Dr Julian Tang, an expert in virus, at the University of Leicester, said treating Covid like flu and other respiratory viruses was perhaps the logical step as society learned to live with the virus.
“We don’t impose any further restrictions for other viruses – we could do the same for Covid,” he said.
His only concern would be for “potential risk” of “long Covid”, Dr Tang added.