I got a 29 on my ACT sophomore year which I stupidly sent to Columbia in advance. The college permits Score Choice and I was planning on just sending my highest scores/removing my lowest from my transcript. Will this 29 be detrimental, even if my other submitted scores are 33, 34, etc? Should I not submit any other scores to columbia before I take the ACT?
You should be just fine. Columbia Admissions only looks at your highest ACT Composite score. Any other scores are either ignored or quickly glanced at to see how much improvement you made from test to test. Besides, a 29 in your sophomore year is not bad at all, especially if your other scores are 33+.