Group Lessons
Many students start learning in a group setting through school programs.
There are many benefits of learning within a group including peer support and competition. As music in essence is about connection and having a 'voice' it is important that the student has a group context.
Group classes keep students accountable to their peers and motivate students to keep up or work harder through healthy competition.
Individual Lessons
Many teachers will say it is impossible to make strict technical progress without one-on-one time with the student (and even more supportive, with the parent).
In a group environment, too much time is lost to give each individual the attention required to correct and foster the appropriate technique. This is simply because each individual thinks and learns differently and what works with one student will not work with every student. In a primarily group setting, many students will develop poor habits that become very difficult to remediate.
The consensus?
The ideal situation for a student is to be attending regular individual lessons with the parent and having a group of friends to play either in a chamber group, practice group or orchestra. Orchestras provide a wonderful development opportunity for students but does not focus on technique or individual growth rather group playing technique (it is a different study altogether!)
In saying this, each child is different so ask the teacher and see what is recommended!