I work at Long Island University in NY. You should start by reaching out to local universities and requesting their criteria for providing credit for continuing education courses. The incentive for most colleges is to offer the course on their campus, collect tuition for each class, and gain campus exposure. The three options that may work for you are:

1.) Reaching out to university continuing education programs and finding out who the director of each program is. If they accept outside resources providing classes for credit, then you could review their criteria and tailor your curriculum to match their requirements. It's important to remember that they may only accept classes taught at their university.

2.) Initiate a partnership between universities and and the school district you teach these classes at, which could then potentially lead to credits since the school district would now have the endorsement of the colleges.

3.) See if you could bring your curriculum to neighboring universities and "increase their scope" in terms of continuing education programs, which could lead to credits being granted for your class.

Again, this is very subjective to each university and how strict they are on accepting outside curriculum, but coming from a school district, I think you may find luck with one of the three approaches above. I'd love to hop on a call to learn more about what you do and possibly help you on this journey if you're interested. Good luck! :)