I am writing to advise you of our appreciation for all of your help over the last few years in supplying the school with cover teachers. You have always been able to fulfil our needs, both at short term and long term notice and communicate with us regarding this.
Apart from these, the main reason for solely using your Agency is because of the hassle free and non aggressive marketing, often employed by other Agencies which has put us off using them.
I hope to continue our excellent working relationship in the future.