Why do my sons not qualify for the earned income credit? They're 17 years of age and still in high school.

If your child turned 17 in 2017, even on the last day of 2017, you do not get the child tax credit.  There are no exceptions to the rule.  You can still claim your child as a dependent.

https://ttlc.intuit.com/questions/1900923-what-is-the-child-tax-credit

Thank you. I understand.