Based on your needs, I found two mindmap tools that could be useful for brainstorming environmental sustainability with your students:

1. Whimsical: This tool offers a range of features like flowcharts, wireframes, mind maps, and sticky notes. It supports real-time collaboration, allowing you and your students to work together on a single document. It also offers AI-powered suggestions for mind maps and a text-to-flowchart feature, which could be useful for your brainstorming sessions.

2. MindMeister: This is a cloud-based mind mapping tool that allows users to create, share, and collaborate on mind maps in real-time. It integrates with popular software like Google Workspace and Microsoft Teams, which could be beneficial if you're already using these platforms.

Both tools are designed to facilitate visual thinking and collaboration, making them ideal for your brainstorming sessions on environmental sustainability.

Based on your query, I found an AI quiz tool that could be useful for your needs:

Quizizz: This interactive learning platform allows you to create gamified quizzes and lessons. It includes a unique feature, Quizizz AI Enhance, which acts as a personalized teaching assistant to help customize activities. The platform supports both teacher-paced and student-paced learning, provides access to millions of pre-made quizzes, and generates detailed reports on student performance. Additionally, Quizizz's AI-enabled quiz generator can automatically create quizzes from existing documents or text. This could be a great tool to engage your students and assess their understanding of environmental sustainability.