All tutors need to speak English during tutoring. This can be a bit tricky to enforce, as many of the learners are more comfortable speaking Xhosa. However, everything they write for school is in English and it really only hurts them in the long run if they are not able to practice speaking it in a safe environment.
This is something that branch coordinators, assistants and the head of tutoring at Branchcom needs to monitor all the time - your returning grade 12s know they need to be tutoring in English but if no one is enforcing it then they will slip back. It's something you will have to do every single tutoring session and bring up in every branch com meeting.
Also, in tutor training, you need to show the tutors how to get each learner writing the responses to questions down, rather than just speaking them. It's in the writing that most learners struggle to articulate themselves, and hence do badly in exams. Unless your learners read, speak and write English constantly while at Ikamva, they won't do well in their matric exams and they will seriously struggle at university with academic English.