According to the Kansas Department of Revenue, those contributions are taxable. Please see below:
The amount you contributed from your salary to the Kansas Public Employees Retirement System is not taxable on your Federal return but is taxable on the Kansas return. Therefore, you must report this amount on Kansas Schedule S, Part A.
To determine the amount to be reported on your Kansas income tax return, you must subtract the amount shown on your W-2 in the wages, tips and compensation income box from the amount shown in the state and local wages income box on your W-2. Some employers will provide this figure for you on your W-2, indicating the amount is KPERS.
https://ksrevenue.org/faqs-taxii.html
