Education chiefs say 88 schools in Suffolk are significantly under-achieving, but will not name them publicly because the information is deemed too “sensitive”.

Almost a third of schools have been given a “red” risk rating by the authority and now face demands for improvement.

The risk rating – unconnected to Ofsted reports – is decided by the county council based on information from the Department for Education and from each school itself.

Eighty-eight of the county’s 299 schools were given the red rating – 61 primaries, nine middle schools and 18 secondaries. The figure is worse than October’s report when 85 schools were given the red rating.

Schools which show the most serious underachievement are issued with a warning notice – a decision which could mean they become academies. Four schools were given the warnings in the latest review on top of the 18 handed them in October.Last night the council refused to name which schools are classed as red, amber and green because of the “sensitive” nature of the ratings.

Headteachers from almost 120 Suffolk schools launched a major vote of no confidence in the council in October following the publication of the first ratings. Teachers demanded “urgent action” be taken to undo the “damage caused” by the report.

Nikki Edwards, assistant director for education and learning for the Conservative-controlled authority, said headteachers were now in support of the reviews and the authority was “heading in the right direction”.

“The heads that get it are really supportive of it; there will be a small number who will not be scared about it but are worried about the process,” she said.

“Any misunderstanding about the process initially by headteachers has been worked on with them. They may disagree with the colour but do now understand the methodology.

“They see it as really positive, they are happy with the support we have got for schools, they are really in support of it.”

That view was contested by Graham White, secretary of Suffolk’s National Union of Teachers branch who said the review was not “constructive”. Although he supported the council in not “naming and shaming” the schools.

He said: “Clearly primary headteachers are going to be very upset about the whole process. Suffolk County Council needs to look at itself and what it is doing and the impact it is having: (the education initiative) Raising the Bar has not had significant impact, the School Organisation Review (move from three-tier to two-tier education) has not had significant impact. What is Suffolk doing to raise standards?”

A total of 135 schools were deemed as “amber” (either positive or negative) – with 76 schools getting the top “green” mark.

Schools given a red or amber negative score have to produce an action plan, setting out proposals to improve.

Sandy Martin, leader of the council’s Labour opposition group, said “nothing” was being done to “bridge the gap” between high-performing schools and schools at the bottom of league tables.

School places:

More than nine out of 10 Suffolk children have been granted their first choice Year 7 school place for 2015/16.

Almost 93% of the 6,717 children who applied were given their preferred school. The figure is a slight fall on 2014/15’s 93.9%.

A total of 98% of Year 8 and 98.7% of Year 9 pupils were given their first preference for the next academic year.

Lisa Chambers, Suffolk County Council’s cabinet member for education, said: “It’s great to see so many young people getting a place at one of their preferred schools. Our school admissions team works very hard to ensure that all applications received by the closing date are given a school place. I’d like to wish all those pupils starting a new school in September the very best as they begin a new chapter of their education.”

The number of applications increased this year by 279.