There are multiple resources available regarding head lice and the various treatment options available. Some effective treatments consist of combing the hair with a metal lice comb and keeping the hair style shorter verses a long style or treating with an over the counter lice shampoo combined with an effective comb to remove any nits.
Consider contacting the local county health department nursing section and speak with a community health nurse regarding treatment options, questions, or perhaps programs that may be available to help provide treatment supplies.
In addition the University of Florida has an integrated pest management (IPM) web site, which has information concerning head lice.
Also, there is head lice information located at the Center for Disease Control’s (CDC) web site.
I would suggest looking this information over and perhaps providing it to the families who have the infestation problem you describe.