Teacher Loan Forgiveness Improvement Act of 2021 This bill modifies the Teacher Loan Forgiveness program by increasing the amount of loan forgiveness available for certain qualified teachers who have federal student loans. The program provides loan forgiveness for teachers who are highly qualified, teach full-time in a low-income school or educational service agency, and complete five years of consecutive service. Specifically, the bill increases from $5,000 to $15,000 the amount of available loan forgiveness for an elementary or secondary school teacher in any subject. It also increases from $17,500 to $30,000 the amount of available loan forgiveness for a secondary school math or science teacher and for a special education teacher.