Is it permissible to sell goods at a party held by the school for Christmas or for celebrating the Messiah, given the need for money?

It is not permissible to sell goods for a private party celebrating the religious festival of disbelievers, due to the Almighty's saying: "And do not cooperate in sin and aggression." Sheikh al-Islam Ibn Taymiyyah stated that it is not lawful for Muslims to imitate disbelievers in their festivals in anything specific to them, nor to sell anything that assists them in that regard, explaining that a Muslim's selling to them what helps them in their festival is a type of assistance in establishing their forbidden festival. As also mentioned in Hashiyat al-Dusuqi, it is disliked to sell food or other items like clothes, or to rent animals, ships, and other things to a disbeliever for their festival.