My Espei Rasboras school very tightly and practically all day. Sometimes they break into smaller schools, but they still school. They even school with my rummy nose tetras and even cardinal tetras. Rummys are great schoolers, but in rasboras (all the harlequins should school the same) are even better schoolers. Plus I think they look better. I like my rummys, but I think their clear/green reflecting bodies make them less noticeable and don't stand out as much in a planted tank. But they are both great together, since rasboras swim at the top, while rummys hang out low to mid.
I've been just a fish only guy with non-planted tanks, but recently started getting into plants and turned the community tank into a heavily planted tank, and I must say the schooling has slowed down majorly, now the raboras and rummys just hang out hovering in the plants like cardinals, they still school sometimes, but not nearly as much in a non-planted tank. And it's not like my fish were in fear of me or anything that caused them to school so much in my non-planted tanks. Just mentioning, kind of bummed the fish aren't as actively schooling anymore, now that it's heavily planted. I won't add a intimidating fish, but will try adding a power head for a current for them to swim against and see if that livens them back up.