Where is the best College to become an ELL teacher?

Seeing that you are in Kansas, a cursory search shows that the minimum requirement is a Bachelor's degree in Education. Once you have obtained your Bachelor's degree, you can move on to an ESL teaching certification program. Most states require a Master's degree in TESOL plus a state teaching certificate (which you would already have with a Bachelor's in Education). The TESOL certification program must be an accredited program approved by the state. Some universities include: Donnelly College, Fort Hays State University, Kansas State University, and Emporia State University. You can refer to this list for accredited programs in Kansas: https://www.ksde.org/Portals/0/TLA/Licensure/Licensure%20Documents/Approved%20program%20By%20Endorsement%2001-14.pdf?ver=2014-01-16-133935-290

Of course when choosing a university you want to consider several factors such as: location, tuition, resources, reputation, etc. Tour campuses and figure out which university is best for you.

I checked the TESOL International website (tesol.org) and was reminded of the great programs in Illinois, also not far from you. One of my favorite professors in a budding grad school program was "on loan" from Southern Illinois University. TESOL includes the following:

The Linguistics Department at the University of Illinois at Urbana-Champaign is one of the oldest, largest, and most distinguished departments of linguistics in the United States, attracting students from all over the world. With faculty members covering all major areas of linguistic research, the department offers a large number of undergraduate and graduate courses, as well as B.A., M.A., and Ph.D. degree programs.