Based on your query, I recommend Midjourney as it offers AI-powered image generation from text descriptions. This feature aligns well with your need for AI tools for drawing.

The key feature of Midjourney is its Text-to-Image Generation. This feature translates text into visual content, which can be perfect for creating custom visual aids for classroom teaching, from diagrams to illustrations. This can help you in creating engaging and visually appealing content for your students.

Another feature that might be useful is the Style Transfer. This allows you to adopt the style of one image into another. You can use this to demonstrate different art styles or create consistent visuals for your lessons.

The Image Upscaling feature enhances the quality of lower-resolution images. This can be useful for creating high-quality educational materials or presentations.

However, please note that Midjourney operates exclusively on Discord, and its interface consists of straightforward text-based commands. This might present a learning curve if you're not familiar with Discord.

In terms of pricing, Midjourney employs a subscription-based model with multiple pricing options. You can choose the one that best suits your needs.

In conclusion, Midjourney offers a versatile and creative solution for your need for AI tools for drawing. It can help you create engaging and visually appealing content for your students.