First, teachers are not trained enough to handle such a class.  Second, limited time to complete the syllabus makes the teachers not to follow such a method.  Third, large class strength makes it practically impossible to follow inquiry-based learning.  Lack of support from the school management could also be a problem.  Parents' lack of knowledge about inquiry-based learning could make them skeptical about the method.  These are some of the challenges that teachers may experience while implementing inquiry-based learning.

Based on my readings and experience, the main challenges include:

1. Low achieving students struggle the most with this method

2. Students may stray too far from the intended lesson

3. Assessment of learning is very difficult

I recommend these two links:

Link 1:  http://inquirylearning428.weebly.com/limitations-of-inquiry-based-learning.html

Link 2:  https://ww2.kqed.org/mindshift/2013/07/03/the-challenges-and-realities-of-inquiry-based-learning/

Thank you for your suggestions and viewpoints.