This term should cover both primary and infant schools nicely.

An infant school is a separate school to a primary school. Most children will start primary school at age 4 (in the academic year of their 5th birthday), however, some areas have infant schools and after Year 2 - when the children are 7 - they will leave that school and attend the closest primary school (or a primary school of their parents' choice if the local council agrees). All primary schools take children from age 4 (some even have kindergartens attached) so even younger. Infant schools are simply schools which have not yet gained primary school status and which take children from their catchment area. For example, the nearest primary school to me is over 3 miles away, but the nearest infant school is only 1.5 mile away.



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Note added at 2 dni  9 min (2009-01-11 11:56:45 GMT)
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http://en.wikipedia.org/wiki/Primary_education



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Note added at 2 dni  14 min (2009-01-11 12:02:10 GMT)
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Personally, I would use another descriptive term for 'poczatkowa' otherwise you are going to be repeating 'primary school' all the time. Elementary schools are more common in the US where they are the equivalent of primary schools (i.e. they take the same-age children). In my answer,I propose to use something like 'elementary', 'elementary-stage', 'elementary-education' in order to avoid repetition of 'primary'.