harry potter - If Durmstrang and Beauxbatons were hidden from common knowledge, how did people from other schools go to them for the Triwizard tournament?

So in GoF, they state that Beauxbatons and Durmstrang are hidden from view and don't have their locations public.

“Durmstrang’s another wizarding school?” said Harry

“Yes,” said Hermione sniffily, “and it’s got a horrible reputation.

According to An Appraisal of Magical Education in Europe, it puts a lot of emphasis on the Dark Arts.”

“I think I’ve heard of it,” said Ron vaguely. “Where is it? What country?”

“Well, nobody knows, do they?” said Hermione, raising her eyebrows.

“Er — why not?” said Harry.

“There’s traditionally been a lot of rivalry between all the magic schools. Durmstrang and Beauxbatons like to conceal their whereabouts so nobody can steal their secrets,” said Hermione matter-offactly.

So how do students get to the other school for the Triwizard tournament?

Answer

Hogwarts was just as concealed:

“But Hogwarts is hidden,” said Hermione, in surprise. “Everyone knows that . . . well, everyone who’s read Hogwarts, A History, anyway.”

“Just you, then,” said Ron. “So go on — how d’you hide a place like Hogwarts?”

“It’s bewitched,” said Hermione. “If a Muggle looks at it, all they see is a moldering old ruin with a sign over the entrance saying danger, do not enter, unsafe.”

“So Durmstrang’ll just look like a ruin to an outsider too?”

“Maybe,” said Hermione, shrugging, “or it might have Muggle-repelling charms on it, like the World Cup stadium. And to keep foreign wizards from finding it, they’ll have made it Unplottable —”

—Harry Potter and the Goblet of Fire

Nonetheless, the delegations from the foreign schools had no trouble finding it. One presumes that Dumbledore could make the location available to the students from Beaxbatons and Durmstrang, if need be. He certainly seems to be able to remove the protective spells around Hogwarts:

As they flew over the dark, twisting lane down which they had walked earlier, Harry heard, over the whistling of the night air in his ears, Dumbledore muttering in some strange language again. He thought he understood why as he felt his broom shudder when they flew over the boundary wall into the grounds: Dumbledore was undoing the enchantments he himself had set around the castle so they could enter at speed.

—Harry Potter and the Half-Blood Prince

A similar situation probably holds with Durmstrang and Beauxbatons: they can simply alter or remove their spells to allow in foreign students. In particular, given that the delegations only arrive on a single day, they would only need to lift their protective enchantments for a very short period.