Purple Comet! is a free, online, international team math competition that has run annually since 2003. Teams of one to six students pick a 90-minute window during a 10-day period each April to solve 30 problems on the high-school-level contest (a separate 20-problem contest is offered for middle school). A teacher or coach registers the team through the Team/Supervisor login portal, and winning teams and full solutions are posted publicly after the contest closes.
FieldsMathematics
AwardsCertificates for winning teams; results and solutions posted publicly after the contest window closes.
You submitA teacher/coach creates a free Team/Supervisor account and registers a team of 1-6 students.