If something is tax-deductible if it happened in the same year, but not tax-deductible if it happened in a different year, you end up with a very uneven system (and a lot of pointless gyrations designed to turn one into having the structure of the other).

For your personal situation, it is not surprising that there is IRS guidance on the topic of education and tax deductibility. The rules have changed several times in the last few decades, but some is deductible: https://www.irs.gov/credits-deductions/individuals/qualified... https://smallbusiness.chron.com/training-costs-tax-deductibl...