Kiddom is free for teachers and students. We’re privately funded and we’ve never really liked time-limited product trials, so use Kiddom for free as long as you want to. There’s also no limit on how many classes or assignments you can make, nor is there a limit on how many students you can add to your classrooms.
P.S. We also don't like the bait-and-switch move either, so rest assured, if you're using Kiddom for free now, you'll be using Kiddom for free later.