To get a student visa for studying in Chicago, your son must apply for an F-1 visa Here's a guide: Apply to a SEVP-approved school in Chicago and obtain Form I-20 Pay the SEVIS fee and complete the DS-160 form. Schedule a visa interview at the US Consulate in Toronto Provide required documents during the interview and pay the visa application fee Wait for visa processing and prepare for travel Check the US Embassy and school's international student office for updates

There's a USCIS office in Chicago, just visit them and they should be able to help , my best bet is an immigration expert