You have no idea how they will react. It can be especially challenging when speaking to a large group rather than to a classmate one - on - one.
وَقَدْ تَخَافُ خُصُوصًا إِذَا تَكَلَّمْتَ مَعَ مَجْمُوعَةٍ مِنْ رِفَاقِكَ لَا مَعَ وَاحِدٍ مِنْهُمْ فَقَطْ .‏