I know you don't care, but you conveniently leave out that Emanuel has proposed increasing the school day in Chicago Public Schools so that teachers would be working an additional 90 minutes per day. When the mayor first proposed the lengthening of the school day, the union announced that they would be seeking a 27% pay increase to cover the extra hours of work. The 30% increase is just about in keeping with what the union previously said. Symphony musicians in professional orchestras also have a union. A conductor or the management cannot just tell the players that they have to rehearse an extra 90 minutes for each program without being paid. The contract may say that if the musicians work beyond a certain number of hours per week, they have to be paid a special rate, similar to overtime.
The teachers see different children every year. They are not there as parents. If they have to work longer, the rules would indicate that they should be paid more. They probably will not get a 30% pay increase, but the mayor just the other day was shown saying that Chicago teachers deserve a pay increase. I take this to mean that he acknowledges that extra work means extra pay.
At my job, I cannot stay over unless I am being paid. The employer is not allowed to ask people to say and to work with no pay. That applies to union contracts as well as to non-union, hourly wage workers who are paid by the hour.