If you currently play a werewolf, you should read up on everything about them, including what, by law, has to happen to them every month. There are no werewolves who are secretly attending the school. The Ministry knows about every one of them. Even Lupin did not secretly attend as the professors knew and covered it up for him.

All information is here.

Every month, they go to the Transformation Habitat during the three days of the full moon (one day before, the direct fullest moon day and the day after). The students (and possibly staff) who are werewolves and go here stay there for the full three days. They are equipped with a Library, study areas, common room and outdoor area with a garden for some fresh air during the day. They are not to return back to Hogwarts during these three days so they are equipped with everything to continue their studies during this time.

All three nights, the werewolves are escorted to separate rooms, which are all empty so furniture doesn't needlessly get destroyed, and given Wolfsbane Potion for their transformations. They are watched by Magical Law Enforcement Squad and Werewolf Capture Unit Officials to make sure nothing gets out of hand, though it doesn't with the potion.

Hogwarts Healers and the Hogwarts Potions Master work on having a full stock of Wolfsbane Potions always and work together with the Ministry to make sure the werewolves stay safe during this time.

Keep in mind that before this came about, werewolves were banned from being at Hogwarts entirely so if someone were to skip out on meeting at the Transformation Habitat at the beginning of the first day, they would be expelled (or fired, if a professor) instantly. Also, there would be no way they would 'escape' as there are highly trained and capable Ministry Officials standing guard over them.

Any thread of a werewolf being a werewolf or transforming outside of the Transformation Habitat will be archived. This means that if you want to turn someone into a werewolf, that must happen during the summer or holidays only (if they decide to go home for the holidays). However, it would be extremely frowned upon still to make other werewolves and considering the fact that the Ministry would know about your character being a werewolf, the Werewolf Capture Unit would be watching your character closely if they know that they aren't at Hogwarts.

Please note that Firenze Academy is not very strict about this and have always accepted other creatures such as vampires and werewolves with open arms.