Are you allowed to trade stocks after you've been an SA?

Cartwrightyes, you can do whatever you want. You are not employed. You are not a registered person with FINRA. Once you start full time though, you may have to liquidate certain positions or change brokerages depending on firm policy.

This is the right answer. One thing you might consider if you plan on holding positions open through your employment next year is opening a bunch of long term positions your senior year (most likely ETF's and solid blue chip dividend stocks or whatever) through a discount broker, since when you return for FT, it's quite likely you will have to switch to a specified broker, and these usually aren't cheap at all. This way, you'll be able to open up an account and take some positions for cheap, and then transfer them over for free (might wanna check with your firm about whether transfers are free or not, but they should be.)