I second this. Both of my children did this, my daughter started in 4th grade. The kits are deceptive, they look like Legos but you can build some remarkably sophisticated robots. With the more advanced ones you can do some pretty advanced programming too. The collaborative way the competition is run is quite clever too. They have a full spectrum of touch points that makes it fairly accessible and satisfying for the children. The other thing I like more than I thought, they provide a couple good starting points for the children to build off of, for the younger kids they are much more likely to succeed by building off of a working plan rather than cutting from whole cloth.

My son has this Apitor kit: https://www.amazon.com/Apitor-App-Enabled-Dinosaur-Building-...

It's similar to Vex in that:

- you use a tablet to control the motor(s) using controls (like a remote controller) or code (like Scratch)

- the motors can be connected to different things (e.g. wheels) depending on how you put it together

- it has sensors as well as motors

I think Vex is a bit more modular in some ways. My son's Apitor kit comes with a proximity sensor and a color sensor, but I think with Vex you can choose which sensor(s) to attach to your build.

I'm a big fan of VEX IQ for elementary and middle school students. Parts are easy to work with, there is a wide variety. Decent array of sensors, and you can program in blocks or Python.

My son has been competing since 6th grade. They got 2nd place at states and loved it, so intense watching them play.