Your tax liability is based upon your income, full stop. Anything you do that causes your income to raise could push your tax liability higher. Working as a 1099 contractor (which is what most lesson teachers are classified as) does not in any way absolve you for paying tax on that income.
If you want to LOWER your tax bill, you need to do one of a few things:
1. Cheat on your taxes (don't actually do this).
2. Deduct all mileage on your car as you drive to and from your lesson teaching jobs (for 2020, 57.5 cents a mile)
3. Deduct your maximum charitable contribution for the year (due to changes in how these are calculated, everyone gets a $300 credit for this in the CARES act, even if you only gave $15 - and this includes tithing at church, unless you can document that you gave more)
4. Call a tax preparer or accountant and see if there are other deductions you can take.
5. Claim your home office space at $5 per square foot. However, a couple years back, the credit for costs for maintaining/building a home office was removed from the tax code until 2025. If you used that home office to work from home for your ISD employer, (even during quarantine) AND to teach virtual lessons, you may not be able to claim it. Get a real opinion from a tax specialist.
6. Supplies for your 1099 work - including reeds, oils. You may need to have documentation to support your claim here.
Those are the big ones that usually apply. However, I am not a lawyer or an accountant. This is not financial advice. Contact someone who does this professionally. You have three employers - you should probably pay someone to do your taxes for you, as it's likely not a TurboTax Free level of work to do on your own.