Sayyed Mohammad Al-Musawi,
Sayyed Mohammad al-Musawi is originally from Iraq and heads up the World Ahlul Bayt Islamic League in London. Other than being involved in various humanitarian projects, he frequently responds to religious questions. In the past, he has also spent significant time in India guiding the community.
It is allowed for Muslims who understand Islam with its evidence to study in schools belong to non Muslims because Islam promotes useful knowledge from any one, but it is not allowed for a Muslim to take part in any non Islamic worship because it is wrong worship and your participation can give wrong message that you approve their worship despite Islamic rule that it is wrong.
Attending school assembly is permissible as far as it does not include a wrong worship. Christian schools keep on claiming that they do not force any non Christian student to attend Christian religious gatherings. If you are under pressure to attend church, you have full right to report those who force you.