This statistical report from the Department for Education sets out the number of offers made to applicants for both secondary and primary school places. It also covers the proportion that have received preferred offers (1st, 2nd, 3rd preference etc).
It is based on the applications made by parents and the offers they received on the respective national offer days of 2 March 2015 (secondary) and 16 April 2015 (primary).
Information specific to the London Borough of Barnet can be identified in this resource, as data is available regionally and alphabetically. You can also use the search function to identify Barnet statistics within each dataset.