Teams are formed by division and compete against teams in the same division and problem. Grade level determines the division for teams in the U.S. and in countries with an educational structure that corresponds to the U.S. Except for Division IV, teams from countries with a different grade system ( "Other International" ) will have their division determined by the ages of the team members. In competition, each school membership may enter one team per problem for each division it covers. Community groups and home-schooled members may enter one team per problem.

The team must compete in the lowest division for which it qualifies. For example, if a team qualifies for Division II it cannot compete in Division III. The team member in the highest grade (U.S.) or the oldest (Other International) determines the team's division as follows:

• Division I -- Grades K-5 (U.S.): Less than 12 years of age on May 1, 2010 (Other International).
• Division II -- Grades 6-8 (U.S.): Less than 15 years of age on May 1, 2010 (Other International).
• Division III -- Grades 9-12 (U.S.): Oldest team member does not qualify for Divisions I or II and is attending regular school--not a college or university or anything similar (Other International).
• Division IV -- Collegiate for ALL TEAMS. All team members must have a high school diploma or its equivalent and be enrolled in at least one course at a two- or four-year college or university.

High school students taking accredited courses do not qualify for Division IV. There is a division finder at online to use to determine the division of "Other International" teams for Divisions I, II and III. No special exceptions will be granted to allow a team to change its division.