We purchased a 3 year Diamond level agreement with KnowBe4 because our cybersecurity insurance provder wanted us to start phish testing staff, among other things.
We do not phish test students. We are an elementary school (grades K-8) and students are already in a walled-garden with email.
I regularly phish test our staff, sometimes once or twice a month.
KnowBe4 has a tremendous amount of content, but it can also be very confusing to understand a lot of it.
It took a little bit of trial and error to create the correct rules in Workspace to allow the messages to come through without being flagged, or marked as spam.
I would recommend the product.