A root word appears. The team on turn has the timer to call out as many forms of the word as they can. Every form they find flips over: +1 point, or +2 for a ★ negative-prefix form. When time is up, the other teams can try to steal one hidden form each. Then it's the next team's word.
Teacher: click a tile when a team says that form. Spelling counts, and both -ize and -ise are fine. Use “+1 valid extra form” for a correct word that isn't on the board.