Would it be more appropriate in a school setting to say, “Walk, please!” for recess crowd control issues, rather than “Walking!” or “Walking feet!” ?

Would it be more appropriate in a school setting to say, “Walk, please!” for recess crowd control issues, rather than “Walking!” or “Walking feet!”

Yes. Or “Please walk,” or “don’t run.”

Walking doesn’t work at all. With very young children, you could say, “Use your walking feet,” which would be akin to “Use your inside voice.”