The Scholastic Art & Writing Awards are open for submissions! Though this competition can be fairly cumbersome to enter (as compared to other national contests, like Bennington’s Young Writers Awards), it can be worth it. There are $5 per category and $20 per portfolio entry fees, but in cases of hardship, those fees can be waived.
I’ve found that the easiest way to get started on this competition is not to click on the main link to the awards, which leads to a log-in screen with no information, but to start with the Local Guidelines & Deadlines page instead. Those pages actually help a beginner to understand what’s going on. The entries are judges regionally, and entries that receive a Gold Key designation then move on to national judging.