Hackney Council has shot down claims by campaigners that air quality tests conducted by experts around Stoke Newington schools are “not fit for purpose”.

An in-depth study was commissioned last year after parents protested against the town hall’s plan to shut streets around Walford Road to through traffic in an effort improve air quality across the wider area and make the Cycle Superhighway 1 (CS1) route quieter and safer.

They believed the scheme would make the air at pinch points worse, pulluting kids at William Patten, Grasmere and St Mary’s primary schools by shifting traffic onto Church Street. The row rumbled on while the tests were carried out by leading air quality organisation Cambridge Environmental Research Consultants (CERC).

An 800-strong petition against the closures was presented a year ago. Last month 60 businesses put their name to the campaign.

Parents also pointed out that the Greater London Authority (GLA) had named William Patten as one of the most polluted schools in the capital – an honour dismissed by transport chief Cllr Feryal Demirci for being based on “very rough data”.

Now, at last, CERC’s mathematical modelling of the scheme’s likely outcome is done – and shows that, while there would be a small increase in nitrogen dioxide pollution at school playgrounds, all except Grasmere would still fall within the national limit of 40µg/m³. The area at Grasmere that exceeds the limit is currently a car park, the council says, but would have levels of 40.9 or 40.1 depending on the options when converted to a playground.

The council says that small rise would be mitigated by other measures, like rolling out the “school streets” scheme at St Mary’s and William Patten to ban school-run drivers; moving the entrance of Grasmere; and installing green screens at all three schools to block harmful pollutants.

None of that has impressed campaigners at CleanAir4Schools, who reckon the exercise wasn’t done properly, and say it underestimates air pollution at the schools as it currently stands because it relies partly on modelling rather than simply taking the readings from discrete monitoring stations at face value.

The council disagrees, saying modelling is actually the most accurate way of determining pollution levels because it takes into account additional factors such as the layout of the built environment – and was based on data from more than 20 monitoring stations in the area. By contrast, the GLA stats seized upon by CleanAir4Schools were based on data from just two monitoring stations.

But there’s more. The campaign group also claims the council is “deliberately” hiding impacts of the road closures by including the benefits of TfL’s new cleaner buses in modelling their impact, but including the older buses in the “baseline scenario”. The council says that’s because the buses were rolled out too recently to have been recorded in the data, collected over 12 months.

CleanAir4Schools’ Sally Newsom said: “This model is not fit for purpose. It seems the council has deliberately hidden the impact, which they say would only make things a little bit worse than today.” Rather, she argued: “The road closures are so harmful they undo [the bus] improvements and even make the status quo worse.”

Environmental scientist and campaigner Tom Knowles also took aim at the report. He said: “In almost 20 years of consultancy I’ve never seen anything so unprofessional. The model has been a complete waste of time and money – it makes it impossible to see the actual impact of the road closures.” He called on Hackney to repeat the exercise or scrap the road closures altogether.

Cllr Demirci hit back, saying: “We’ve got to be brave in getting more people out of their cars. That means making our borough even better for walking and cycling with proposals like these. No scheme is perfect, and limited money means we can’t do everything we want to at once, but I want to reassure residents we are fighting to transform our borough by reducing car use, improving walking and cycling conditions, tackling air pollution and lobbying to make our borough a place for people, not cars.”

She also revealed a bid had been submitted to Sadiq Khan’s Air Quality Fund, which could see Church Street become a “zero emissions zone” that only buses or ultra-low emissions vehicles (ULEV) would be allowed in at certain times.

The proposals go to cabinet this month.