From The Student Art Guide: See the Full list of art competitions you may likely be eligible to compete in here!

Competitions can be a goldmine for Art students, offering money, scholarships, product vouchers, overseas trips, promotional opportunities and other prizes. With digital submissions common, those in disadvantaged countries can often compete on an equal footing, winning prizes that convert handsomely to a local currency. As well as the monetary benefits, prizes and awards can provide excellent fodder for university applications or CVs/resumes. The fame and social media attention garnered from a winning entry can also be just what is needed to launch a creative career.

Many high school students fail to enter art competitions, as they are daunted about the standard of work required (especially after viewing technically outstanding entries such as Shania McDonagh’s drawing above). They worry that their artwork would never compare to this and that they have no chance of winning; deciding the competition is not worth their time and effort. If you worry that you are not good enough, it is worth remembering that:

No one needs to know that you have entered. You have nothing to lose and everything to gain.
Everyone else has the same fear as you, so the number of people who enter is surprisingly low – especially for competitions that are less well known (like many of the ones on this list). Of those who do enter, many are ‘whole class’ submissions, where a teacher has required whole class participation. Your serious competitors are far fewer than you think.
Judges sometimes favour unexpected work – it is not always those who produce exceptionally realistic artwork who win. Your creative approach might be just what the judge is looking for.
You may have already produced appropriate work as part of a school project or may be able to tailor an upcoming school project around a competition brief. Digital submissions can also mean it is possible to enter multiple competitions using the same work (check particular rules of each competition to make sure this is allowed), so this can mean that much less time is required to submit an entry.