"acada szn" means exam or academic crunch season — the period in the school calendar when studying becomes everyone's top priority and social life temporarily shuts down. It is one of many casual words teens pick up from friends, social media, music or sport, and on its own it carries no particular warning. If you hear your teen use it, it is fair to ask what they mean by it in their friend group, since meanings drift quickly. Asking out of curiosity rather than alarm tends to keep the conversation open and useful.