Today, the stock TWOU dropped by 70% today. What are the elements to analyse in the SEC filings to predict such a movement?
The elements I would use would be the "Risk Factors" to understand catalysts for re-valuing a company's share, along with the costs they incur to facilitate growth.
A quick glance at TWOU suggests they have spent a lot on acquisitions, and have borrowed a lot of money to do so. So by having a decent quarter but announcing that they aren't going to launch their programs, and plan to do even less launches, then it isn't clear to some large investors how they plan to pay for their debt, LET ALONE actual shareholders. So they sold. The only people that got paid are the companies they acquired, acquisitions they aren't going to quickly launch products for and might not ever.
Being in the risk factor and financial statements this was always a possibility, so you could have been hedged with puts, but the SEC filings wouldn't have let you know that today would be the day they announced a pivot and that simultaneously other large investors would sell the stock off 70%. It might be more accurately valued for a statistically good investment at this point, or the low value may hurt their future financing opportunities if they need to pay their debt off with share dilution and secondary offerings.
All you can do is try to predict human behavior with this information.