Mrs Colmer, who came to Winslow in September 2016, is retiring to spend more time with her family and friends.
At a special assembly on Monday, children – dressed in their own clothes to keep cool during the heatwave – presented Mrs Colmer with a leaving book, flowers and gifts.
They performed some of her favourite songs and hymns, and poems were read out in her honour.
Mrs Colmer said: “It has been an absolute privilege to serve Winslow as the headteacher of its primary school. The pupils and staff are wonderful and I will miss them all.”
After graduating with a degree in history, Mrs Colmer first worked as a staff manager with M&S before becoming publicity manager at Hodder Christian Books.
It was only after working as a learning support assistant at her children's school that she became fascinated with the ‘new style’ maths she observed, and caught the teaching bug.
Her first teaching role was in 2000 at Swallowdale Primary School in Melton Mowbray. She also taught at Long Meadow School, Milton Keynes, and Waddesdon Primary School before joining Winslow six years ago.
In her time at Winslow, she has always stressed the importance of the school being at the heart of its community and is delighted to have seen the school grow as families have moved into new housing in the town.
Recognising the impact that the Covid pandemic has had, with its disruption to learning, a key focus has been to 'Reconnect the Rainbow' - supporting children to readjust to normal school life and get back on track, emotionally and academically.
Mrs Colmer is particularly delighted to see Rainbows Pre-School expanding to offer the community some afternoon sessions from September 2022.
Mrs Colmer, who has been married to husband Geoff for 38 years and has two grown-up sons, said she is planning to relax and live life at a different pace of life, although she is certain her grandchildren will keep her busy.
School governors have appointed Samantha Dimbleby, deputy head of St Mary's Church of England School in Aylesbury, who is also currently acting as interim headteacher at Westcott Church of England School, as Mrs Colmer's replacement when children return in September.