An extra class of pupils will start at Brighton and Hove's most popular secondary school in September after 28 parents successfully used an appeals process to win places for their children.

Dorothy Stringer School in Loder Road, Brighton, will be forced to expand after an independent appeals panel decided it had a higher pupil capacity than the 308 originally agreed with Brighton and Hove City Council.

The move has infuriated Dorothy Stringer headteacher Trevor Allen, who will now be expected to take 336 pupils.

The news has also come as a shock to parents whose children missed out on places at the school when they were initially allocated by the council. Some of their bids might have been successful had the extra 28 spaces been available at that time.

Mr Allen said: "I am staggered by these decisions, the school has taken extra pupils for the past three years and is already full to bursting point. This will mean increasing class sizes and is bound to have an impact on learning.

"We would contest this if we could but there is nothing we can do about it."

The council confirmed this week that across the city more than 140 families have lodged appeals because they were unhappy with which the secondary schools their children have been allocated.

So far the appeals panel has ruled on 56 cases, all of which involved parents who wanted their children to go to Dorothy Stringer.

A council spokesman said the panel came to an independent decision that the school could take on the extra pupils without a detrimental effect on education.

It then assessed the merits of all the appeal cases and offered places to the most worthy candidates.

The spokesman said the places were not allocated to the children living closest to the school, as they would have been under non-appeal circumstances.

Tracey-Ann Ross, from campaign group Schools 4 Communities, said this had upset several parents.

She said: "It is wrong that some children have missed out this way. It is also a sad thing that some parents and children have been put through appeals that ultimately should not have been needed."

The catchment area for Dorothy Stringer and neighbouring Varndean School was one of the most divisive issues in controversy earlier this year about a new school admissions scheme the council will bring in for September 2008.

The year group starting secondary school in September will be the last to be allocated places under the existing system, which gives priority to children who live the shortest distance from schools.

Before the increase Dorothy Stringer's intake was already the second largest of the city's nine secondary schools. Cardinal Newman Catholic School will take 341 pupils this year.

Dorothy Stringer was massively oversubscribed when families submitted their secondary school admissions application forms last Autumn. It was listed as the first choice school for 481 pupils, meaning 173 had to miss out when the council announced its allocations in March. The council said the decision that extra capacity was available applied to this year only. It said the school would not necessarily be expected to take more pupils in future years.

Mr Allen said that regardless of his dislike of the situation all new pupils would be welcomed by the school in September.

Have you been involved in an admissions appeal? Post your comments below.