the Smithsonian staff cited the "Neutrality" of the government facility as a reason for asking the students to remove their hats...it wasn't until legal action was threatened did the communications director defuse the situation with that apology.
Given that the chaperones contended the unique hats were for identification of their students...which is a credible reason...I suspect that the Smithsonian staff realized it didn't stand much of a chance in court and did what they could to forestall any further trouble.
That being said, since people of all faiths and political persuasions frequent our national museums and just want to comfortably see the unique sights, it is my contention that political signs should not be paraded there...just imagine a large group of Pro-Lifers with distinctive wording on their hats run into an equally large group of Pro-Choicers with Vagina hats stating their allegiance arrived at the same time after a Rally/Counter Rally on abortion...do you see the potential for an uncomfortable experience?...not just for the proponents/opponents, but all the other un-aligned visitors?
It is clear, at least to me, that the group in question was trying to expand their 'mission'...since they were inside, there was no need to wear those hats and could easily have taken them off...also, chaperones are there for the express purpose of watching the kids...not letting them roam free.
The teachers/chaperones were needlessly pushing the envelope...and disrespected the desired neutrality of the Smithsonian.
Link: https://www.foxnews.com/media/catholic-school-students-kicked-out-smithsonian-museum-dc-pro-life-beanies