Hyphens, En Dashes, Em Dashes

Q. Can Chicago please provide clarification on hyphenation when “high school” is used as an adjective? For instance, do you prefer “middle and high school students” or “middle- and high-school students”? Why? One never sees “high-school curriculum” or “high-school classroom” in educational writing, but I don’t fully understand how the rules are applied toward permanent compounds used as adjectives in CMOS. Thank you!

A. It wouldn’t be incorrect to write “middle- and high-school students.” But both “middle school” and “high school” are listed in Merriam-Webster as unhyphenated noun phrases; when they are used attributively, they can remain unhyphenated.

In general, any compound that’s rarely hyphenated in real life can remain unhyphenated as a phrasal adjective if the meaning remains clear without the hyphen. This goes double for any compound that’s listed in a dictionary without the hyphen. So write “middle and high school students.”

On the other hand, if a compound is listed in the dictionary as a hyphenated phrasal adjective, Chicago style gives you permission to drop the hyphen in most cases when the compound follows the noun that it modifies (see CMOS 7.85). For example, a high-strung high school student would be, according to Chicago style, high strung (contra Merriam-Webster).

For specific examples and common exceptions, consult our hyphenation table at CMOS 7.89. If you’re still in doubt, hyphenate before the noun but not after.