62. 50% of salary when sick leave is exhausted?

When an employee has used up all of their sick time, PNL & vacation - we still pay them 50% of their salary. Can we renegotiate that? There doesn't seem to be much of an incentive to come to work when you can still get 50% of your wages for sitting at home!
If an employee has used all available leave, they only receive the 50% differential pay while they are off due to illness.   If they are off work for PN or vacation, they are docked full pay.  The 50% differential pay is Ed. Code, so we can not change it.