Maxie Allen and Rosalind Levine made comments in a WhatsApp group towards Cowley Hill Primary School
Maxie Allen, 50, and Rosalind Levine, 47, were detained for 11 hours after by six uniformed officers in January on suspicion of harassment, malicious communications and causing a nuisance on school property.
The parents were arrested after Cowley Hill Primary School in Hertfordshire, where their daughter attended, complained of a high volume of emails and disparaging comments on WhatsApp.
But Hertfordshire Police have since admitted unlawful arrest and have paid out £20,000.
Allen, a Liberal Democrat councillor, told The Times: "We're very pleased Hertfordshire constabulary have recognised, albeit belatedly, that our arrests were unlawful.
"I hope the debate around our case has a positive effect on how these issues are handled in future. The police should not be a tool for public authorities to close down legitimate comment and scrutiny."
The saga allegedly began in May 2024 when Mr Allen, a former governor at the school, questioned why an open recruitment process was not carried out, hoping a meeting would be arranged to discuss.
But his worries were left unanswered and "inflammatory and defamatory" comments from the parents were later seen by the school.
They were banned from entering the premises including being blocked from attending the parents' evening for their daughter Sascha, 10, who suffers from epilepsy and is neurodivergent and registered disabled.
Hertfordshire Police received a complaint from the school in June last year relating to a social media campaign by the parents, and again in December, complaining of “persistent” calls and emails.
Allen and Levine say that they emailed regularly to address issues relating to Sascha's needs and repeatedly tried to persuade the school to overturn the ban.
Levine used WhatsApp to make a disparaging comment about the acting head teacher at the time and cast aspersions on the abilities of the head of governors, according to the newspaper.
A police officer issued a warning to the couple in December and advised them to take Sascha out of the school, which they did the following month, a week before they were arrested.
Hertfordshire Police originally defended its arrest but has now agreed a £20,000 payout after admitting that the legal criteria for arrest was "not made out' and formally accepted liability for wrongful arrest and detention.
Chief Constable Andy Prophet said that the inspector who approved them did not believe Allen and Levine would consent to a voluntary interview and also needed to preserve electronic devices.
But the force's lawyers admitted that the criteria for arrest, under the Police and Criminal Evidence Act, were not made out "therefore rendering the arrest unlawful."
The force agreed a payout of £10,000 each to Allen and Levine, noting that the sum was "significantly above that required by the case law and reflects the constabulary’s desire to bring matters to a conclusion."
Mr Harris added: "The next step, for Hertfordshire and other forces across the country, is to learn what went wrong and never repeat this mistake.
"A good place to start would be a recognition that the criminal law is not a tool for protecting delicate feelings, or wounded reputations, and officers must not allow it to be abused in this way."
In response, the force conceded only that the arrest was wrongful, not the investigation.
A spokesperson said: "Whilst there are no issues of misconduct involving any officer in relation to this matter, Hertfordshire Constabulary has accepted liability solely on the basis that the legal test around necessity of arrest was not met in this instance.
"It would be inappropriate to make further comment at this stage."
