Up to 70 four- and five-year-olds could miss out on reception places if two Surbiton schools are not expanded.
A report to councillors ahead of a vote next week says if they do not approve expansion of Maple Infants' School and St Andrew's and St Mark's Junior School 70 children could miss out in 2017/18.
Thirty extra pupils a year would enter Maple Infants' from next September if the plan is approved.
Earlier this year expansion plans faltered when Kingston Council decided against building a new two-storey classroom block, after parents voiced concerns over its design.
A "bulge class" is to enter Maple Infants' this September.