Scores of children in Earlsfield have been unable to secure a preferred primary school placement, while just under 30 children in the borough still have no place at all.
Following a meeting last week, Smallwood Primary School in Tooting will take on a 30-pupil "bulge" class - one-off extra classes that start in reception and progress through the school but are not permanent.
In Southfields and Earlsfield only 56 per cent of parents got their first choice of school and in Earlsfield 27.5 per cent of children did not get their first, second or third choice.
The council has been heavily criticised by the opposition party, Labour, for selling off some of the best primary school sites to be turned into luxury sites and for a lack of forward thinking.
Earlsfield Primary School received 334 applications for just 60 places
Alex Sykes, an editor at Mumsnet Wandsworth, said: "Our members in Earlsfield are pleased the council has listened to their concerns about the distance their children will have to travel to school.
"But they, and the parents of children already at Smallwood, are worried about how the arrangement will work in practice.
"Smallwood's intake was doubled just a few years ago and parents are worried whether it can cope with another additional class, especially as it appears this is being arranged at the eleventh hour."
Councillor Kathy Tracey, cabinet member for education and children’s services, said: "I think parents will be happy. They have a lovely playing field and they have good grades.
"It is a nice building. They have got space for all the extras but will have to put in a temporary class room."