Is it permissible to forge school documents for the purpose of religious study abroad, especially if the student is not from an Arab or Islamic country?

The default rule is that forgery is generally impermissible. It has two scenarios: The first is when forgery is used to attain a legitimate right for which all other avenues have been blocked; in this case, it is permissible, and the sin falls upon whoever obstructed the person from their right. The second is when it is used to attain something false, and this is not permissible.

As for religious study, it is both a right and an obligation. If a person can acquire it through legitimate means, then forgery is forbidden for them. However, if they find no way to acquire it except through forgery—which is a far-fetched assumption—then it is permissible for them, and it might even be obligatory, because that without which an obligation cannot be fulfilled is itself an obligation.