My only form of photo identification is my school ID card. Is this acceptable?
Yup! I always used school ID (until I got my license… then I used that just to be cool :D).
"Current official photo ID
Must be an original, current (valid) ID issued by a city/state/federal government agency or your school. Note: School ID must be in hard plastic card format. Paper or electronic formats are NOT acceptable. Your first and last names must match the ticket. The photo must be clearly recognizable as you. "
https://www.act.org/content/act/en/products-and-services/the-act/test-day.html
(scroll down to “Acceptable Forms of Identification”)