Ash-Shaykh Zayd al-Madhkali, may Allah have mercy upon him, was asked the following question,

:أحسنالله إليكم, يقول السّائل من فرنسا:ما حكم قراءة القرآن جماعة؟

The Question: What is the ruling of reading Quran in congregation?

الشيخ:قراءة القرآن جماعة, إن كان المعلّم يعلّمهم ويلقّنهم, يقرأ بصوته وهم يتبعونه منأجل الإتقان و الحفظ و عدم اللّحن, فلاحرج.

The Answer: “Reading the Quran in congregation;  if it is a teacher teaching them Quran and making them say it after him, such as he reads with his voice while they follow him for the purpose of perfection and memorization and in order not to error then there is no problem.”

أمّا إذا كانوا بدون ذلك,يجلسون جماعة,ثمّ يقرؤون بصوت واحد,مطلع واحد وموقف واحد فهذا من البدع الصّوفية,لا يقلّدون فيها,ولا يجوز هذا العمل,عمل بدعة.

“As for if it doesn’t include of that , whereas they sit together then they read with one voice,  with the same starting point and ending point, then this is from the innovations of the sufis, they shouldn’t be blind-followed in it nor is this action permissible, it is an act of innovation”

Reference: ad-Durar al-Bahiyyah , tape (2).