We wish to take issue with Paul Ramsden's argument concerning the Centres for Excellence in Teaching and Learning ("A poor policy poorly managed leaves little to show for ?315 million", 15 March). We also dispute the Cetl evaluation report's finding that the centres have not delivered material changes beyond those institutions that received funding ("Cetls' impact assessed: the sector hardly felt a thing", 15 March).

We challenge these statements on the basis of our experience as co-directors of sigma, a Cetl specialising in mathematics and statistics support, established to address serious national concerns about the preparedness of incoming undergraduates in many disciplines.

From the outset, sigma operated beyond the two institutions (Loughborough and Coventry universities) in direct receipt of Cetl funding. Two years after the end of that funding, it continues to operate: both host institutions have committed significant ongoing finance for its activities and it has secured external funding to continue promoting maths and statistics support across the sector at a time when the nation's quantitative skills continue to cause concern.

Internally, sigma can point to many lasting achievements. Beyond the host institutions, its impact has been significant.

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It has provided pump-priming funds and a wealth of resources and advice to enable maths support to be set up in 17 universities. It has helped the Wales Institute of Mathematical and Computational Sciences in establishing eight centres at Welsh universities. It has created a network of six regional hubs, covering England and Wales, which provide opportunities for staff development and the sharing of good practice. It has advised the Scottish sector and facilitated a network of support providers there. Further afield it has aided the development of the Irish Mathematics Learning Support Network and worked with colleagues in Switzerland, Sweden, Germany and Oman on setting up the first maths support centres in those countries. We could go on.

Maths support is now firmly established in the sector, with many universities highlighting their provision in their access agreements. The thousands of students who have been helped to succeed in institutions across the world in disciplines from anthropology to zoology would not share Ramsden's judgement that the funding provided to sigma has been "frittered away".

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Tony Croft, director, sigma Loughborough University

Duncan Lawson, director, sigma Coventry University