What are some typical group projects for 7th grade science?

have them build a functional thermonuclear device that only lacks nuclear material and inertial explosives, making them a target for iranian agents trying to recruit them for their nuke programme.
they get abducted by the iranian spies, incarcerated in a cave to build a nuke for them, and now must work together and use their SCIENCE! to defeat the iranians and save the world from nuclear destruction!

Three junior high science fair projects that I remember:

Every year, at least two people built a tornado machine.

Sprout seeds with a light bulb underneath, to see if light or gravity determines whether they grow up or down.

Galileo’s gravity experiment – test if objects of different mass fall at different speeds.

We added 2HCl (hydrocloric acid) to sea shells and captured the CO2 released. https://practicum.melscience.com/experiments/seashells-in-hydrochloric-acid.html
That was chemistry. If your class is just doing biology you might want to do something else. We had to work in groups of two to dissect worms in biology.