This paper assesses the impact on economic growth of increased efficiency of public spending in primary and lower-secondary education. Higher efficiency in public spending in schools can bolster growth through two main channels. On the one hand, it can allow a transfer of labour from the public sector to the business sector at unchanged educational output. On the other, it can enhance educational output and productivity of the future labour force at unchanged public employment and expenditures. The paper argues that, in most cases, efficiency gains might have larger effects on GDP in the long run if they are used to increase educational outputs rather than to reduce inputs. A 10% increase on educational output might raise GDP by, on average, 3% to 6% in the long run in most OECD countries, whereas using efficiency gains to transfer resources to the business sector might have an impact of less than 1% on GDP. However, some trade-off can appear in the short run because input-decreasing efficiency gains materialise more rapidly on growth than improvements in output-increasing efficiency. (A bibliography is included. Contains 12 footnotes, 3 figures and 2 tables.)