Who should be provided as an academic reference for job applications?
Your academic reference should be a teacher you have taken a class from or worked with in another academic capacity like a research assistantship, an academic internship, etc.

For students very early in their careers who have only taken large lecture classes, this can be challenging. Some teachers of large lecture classes have concrete guidelines for when they will recommend students in these classes (e.g., I might have a policy of recommending any student who achieves more than a 3.7/4.0). You might look at your professors websites or ask them. The professor will likely review your work in the class before writing a letter so you will be wise to pick a professor of a class you did extremely well in.

Alternatively, you might be able to ask a post-doc or graduate teaching assistant that you worked with more closely with who is familiar with your academic work. I wrote these letters for undergraduates when I was a graduate student. Graduate student letters would be inappropriate for applying to a graduate program but should be just fine for intra-University programs and placements.