Its interesting how the teachers can decide to only work what they are required to do and that makes it unsafe for children to be at school.  
Teachers are only required to work about 7 hours a day five days a week for 39 weeks of the year.  So a teacher with 10 years experience makes 92000 a year working 7 hours a day for 39 weeks of the year.    That's around $67 per hour.  Good teachers work a lot more then the required hours.  I understand that so please no comments about how many hours extra they work, I know...But lets make the required hours a teacher has to contractually  work enough to make schools function well.  
Please negotiate a contract with the teachers that requires them to work the number of hours needed to ensure kids are "safe" at school so that when teachers decide to "work to rule"  Schools should function as normal.