Student Agriculture Protection Act of 2021 This bill modifies the requirements for calculating taxable income to exclude from the gross income of a student agriculturist up to $5,000 of the gain from the sale or exchange of personal property (including livestock, crops, and agricultural mechanics or shop products) produced or raised by the student agriculturist. A student agriculturist is an individual who is under 22 years of age and is enrolled in (1) an FFA (Future Farmers of America) chapter or a program established by the National FFA Organization; (2) a 4H Club or other program established by 4H; or (3) a student agriculture program that is under the direction or guidance of an agricultural educator, advisor, or club leader.