I find fish school best when there is something to be cautious about. I don't advocate purposely scaring your fish. Instead I say be happy knowing that they are not upset. That said there are other ways that schools seem to get stronger. If you have a larger tank and more individuals in the group for instance.
As mental exercise imagine 100 neons in a swimming pool and now imagine that the pool has low visibility think blackwater. Now imagine yourself as one of the neons. You are very low on the food chain, birds, frogs other fish all form very real threats would you rather be in a group of your own kind or on your own? The fish would be in constant fear of loosing their group getting eaten or any number of other fears.
Now I might be over thinking it all, but when you think about it. We kind of do the opposite thing. We put them in aquariums, hopefully free of predictors (lol). Clear water so we can enjoy them. Plentiful food so they can have there best life and show us the best versions of themselves. Well in that case there is little to worry about for the fish and they can always school up if they need to, as they can easily see each other.
I'd say not only don't worry about it, but celebrate the fact that they don't feel the need to.
