بسم الله الرحمن الرحيم
In itself it is lawful to teach the holy Quran and take the remuneration. However, it is better to teach it without fee but the problem is that people would not take it seriously and the children and their family shall pay less attention. Thus it is alright to charge some fees. However, you should also have the provision to keep the poor students exempted from fee. When you collect the money and you do not need it then you should use it in charity and other good deeds.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.