If you have some money to spend, you can buy her one share of stock from
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. I purchased one for a teacher that retired who was a favorite of my children. I bought her one share of apple stock and had the plaque read "One last apple for the teacher." She cried.
You could fly an American Flag over the school on a day that you later name in her name and then present the Flag to her in honor of her service to the school. Better yet if you contact your Congressman they will fly one over the Capitol building in DC for you and send you the flag and a certificate.
My other idea is if you have someone "artsy" who can take a photo of the school and do a pen and ink of it and frame it with a plaque for her. Something she might enjoy hanging on her wall at home. I think there are even computer programs you can buy that will change a photo into a pen and ink drawing .... d
In addition to the above suggestions, you could host a coffee/cake reception one evening in May so parents and children can have a chance to say "good-bye". Be sure to invite the principal's spouse to attend as well.
We did the same thing. Our principal was practically a legend in the district and retired after about 20 years in that school, having been the principal since the building was opened. The school library was renamed in his honor.
I'd suggest something along that line - something that will last for years. You could name the library, gym, or other space or plant a tree or add a bench with a plaque dedicating it in her honor.
Sure, why not try to name an area of the school in her name. For example, our retired Principal from a couple of years ago really focused on literacy, and as such the school Library. We ended up naming the school Library in her name. We had the art teacher stencil the new Library name above the Library at every entrance. We also went so far as to have this dedication entered into the city records, so it is official.
This really meant much to her, and cost us nothing.