I am a retired teacher who has been hired as a consultant for a school system. I am being paid when I submit a voucher for my services. The district is not taking any taxes out, and informs me that they will not and it is my responsibility to pay taxes on this income. Is there a form for me to file?

You should plan on filing (a) estimated tax payments (1040-ES) in April, June, September and January, and (b) filing schedule C and Schedule SE as a self-employed worked when you do next year's taxes. Basically you are responsioble for paying income tax and self-employed tax (social sscurity and medicare) on your wages. I suggest you read the following link:
Self-Employed Individuals Tax Center