Even when you proof, get someone else to proof, use spellcheck, grammarcheck, backup spellcheck, there’s invariably one that everyone/thing missed. It will happen again in college papers, in professional presentations, etc. Avoid it as much as possible, be suitably embarrassed when it happens (which it will), and then move on.
Now sending an essay to Rice that says, “I believe I will thrive with Brown’s Open Curriculum” is inexcusable.