Thanks everyone! After talking with him yesterday at pick up, I still did not get the feeling that he 'got' what I was saying. I understand that YOU can not drop things at work and be here, but you need to understand that I can not drop my family life to accommodate lateness.

Not satisfied with his response. I sent a notice home via email last night , reiterating that I close at 6pm and am often leaving the house right behind them for other obligations. No exceptions. No excuses.