Tardy First Graders

Question:

Dear Jane and positive discipline associates,
I teach an extended day program for first graders who are in need of extra help with reading and math. The program began with a four week summer session. Tardies were rarely a problem because school began at 8:45. Now that we are on a regular school schedule, our Project H.E.L.P. program begins at 7:30 a.m. I realize this is an adjustment for families, but only one student has been consistently on time. The other nine children have been from five to ten minutes late every day this week! Because we only have 30 minutes together, it’s critical that the kids arrive on time. I have one parent who is now considering taking her son out of the program because of the early start time, and the resulting phone calls from me when her son is absent/late.
I am feeling frustrated with and unsupported by the parents of these children. I am trying to be empathetic to the parents’ perspective, but I don’t have children of my own. I’m a new teacher. What approach do you suggest I take with the parents?
Thank you for your help with this problem. I appreciate it! Barbara