[nobe-l] question

[Faith Manion]

Hello all,
I am currently completing my student teaching in an 8th grade English classroom.  I ran into a situation yesterday and I was hoping you all might be able to provide some suggestions.  The students were working in groups and I was monitoring the groups.  Afterwards, my teacher informed me that about three of the students in the classroom were not engaged in their groups.  How can I find this out in the future?  What's a good way to ensure all the students are participating when doing group work?
Thanks 
Faith