I don’t know about this “clear right” the school administrator is talking about.
First, because in almost all cases, the property is the parents’. They didn’t do anything or have full control over the events that led to the confiscation.
Such a transfer of ownership would need to either be in a star, or proven to be such a ubiquitous common practice as to be implied and assumed by both parties.
Second, because it is not great chinukh. What will students pick up about the importance of respecting other people’s right to property (baalus)?
But the two cases differ:
A school is a chinukh institution. Parents expect it to take measures necessary for that chinukh. If this is common practice, it may be implied when hirng them to be your shelichim for chinukh and teaching them what they need to eventually get hired and to live in this world.
In contrast, I know our shuls today are Batei Medrash, but does anyone join a shul expecting any chinukh measures, that we can discuss whether ones that cost money are implicitly included?
For that matter, we generally consecrate them as Batei Medrash in order to permit camaraderie-building activities. Often to include food and drink.
I don’t think this implied part of the membership contract (which I questioned above anyway) would hold for a shul.
I find the use of “has the right” ironic. Halakhah doesn’t have a concept of rights. The nearest we do have, which is similar enough, is that violating a right is seen as a kind of theft: geneivas Daas, gezel shinah, the discussion of whether cheating someone out of their choice of which kohein to give terumah to is taking something of monetary value, etc…