Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Reading the Quran together in unison is not permissible because it is not mentioned in the Sunnah. And if it is done in a loud voice that disturbs those who are remembering Allah and sitting there, then it is even more disliked, because of the general meaning of the words of the Prophet (peace be upon him): “When one of you stands in prayer, he is conversing with his Lord, so let one of you know what he is saying to his Lord and do not raise your voices above one another in reciting when praying.” (Ahmad)
Answering your question, the Fatwa Center at Islam Q and A states:
Reciting Quran Together: Scenario 1
If what is meant is that they recite the Quran together in unison, pausing and stopping at the same time, this is not permissible, and at the very least it is makruh (disliked). This is because there is no report from the Prophet (peace be upon him) or from the Companions that they did that.
But if that is done for the purpose of teaching, then we hope that there is nothing wrong with it.
Reciting Quran Together: Scenario 2
If what is meant is that they gather to read the Quran in order to memorize it or learn it, and one of them reads whilst the others listen, or each of them reads to himself without raising his voice or reading in unison with others, then that is permissible. The Messenger of Allah (PBUH) said: “No people gather in one of the houses of Allah, reciting the Book of Allah and studying it together, but tranquility descends upon them and the angels surround them and mercy covers them, and Allah remembers them to those who are with Him.” (Muslim)
Allah Almighty knows best.