You would receive a 1099-MISC form showing this money as Nonemployee Compensation in Box 7.  This is self-Employment income and will be entered as SE income when you file.  You can deduct various expenses related to this income, including any supplies you buy for your classes.  You may also have a home office if you have dedicated space at home to prepare for classes.

If you show a profit on the Schedule C you will file, then you would pay regular income tax on that profit plus Self-Employment taxes.  SE taxes are simply social security and medicare that was not withheld by an employer as it is on a W-2.