Mr Wehr-Candler said the window was a very impressive piece because of its size.
"It's also a historic window because it would have been one of the last big windows to be made at Harry Clarke Studios, I suspect in the 1960s, before they closed down."
And it was an example where overseas work didn't always get the presentation of New Zealand flora and fauna right, he said.
The window depicts scenes from a number of legends surrounding St Patrick as well as incorporating some New Zealand images including iwi, flora and fauna.
A website www.harryclarke.net said Harry Clarke, who lived from 1889 to 1931, was "undoubtedly Ireland's greatest stained glass artist".
St Patrick's School and church have been sold and Our Lady of Kapiti Parish have been creating a new school, Our Lady of Kapiti Parish School, in Milne Drive.
The finishing touches are being applied to the school, which will be open for the new school year, and then planning will get underway to create a new church next to the school.
Our Lady of Kapiti Parish School principal Martin Elms said the purpose of relocating the window was to preserve it for the future as well as "enable it to be readily available for the school, parish, and wider community to enjoy and learn from for many years to come".