The most recent school census (January 2016) shows that 520 nursery pupils were attending free schools. The census is available here: https://www.gov.uk/government/statistics/schools-pupils-and-their-characteristics-january-2016
This census does not include data for the 20 primary free schools that opened in September 2016. The number of nursery pupils attending these schools will be included in the January 2017 school census, which is due to be published in June this year.
In January this year the Department announced £50 million of capital funding to help create almost 9,000 new places for children eligible for 30 hours of free childcare. This will support the expansion of a range of nurseries and pre-schools, and we expect free schools to make a modest contribution to the creation of additional nursery places.