Yes, back-to-school is hyphenated when used as an adjective phrase before a noun, such as "back-to-school shopping."
No, "high performance" is not hyphenated when used as a noun phrase, such as "high performance is important." However, when used as a compound adjective before a noun, it is hyphenated as "high-performance," for example, "high-performance vehicle."
Yes, "school-age" is typically hyphenated when used as an adjective before a noun (e.g., school-age children).
The term "high school" is a compound noun, with a distinct meaning (secondary education) separate from simply a school that is high. It can also be used as an adjective/noun adjunct for things associated with high schools (e.g. high school teacher) and is usually not hyphenated.
If you're using "after-school" as an adjective (e.g. I participate in an after-school program -- after-school is describing the kind of program I participate in), then it is hyphenated.If you're using "after school" as an adverb-noun phrase (e.g. Meet me after school -- after school tells when to meet me), then it is not hyphenated.
Yes, "pre-school" is a hyphenated word.
Fine-tune is an 8 letter hyphenated word. High-tech, half-mast, half-moon are additional hyphenated words.
Heart-to-heart and half-baked are hyphenated words. Additional words include high-minded.
The hyphenated non-school would be correct, but would be an unusual usage.
Yes, "school-wide" is hyphenated when used as an adjective to describe something that pertains to the entire school, such as "school-wide event" or "school-wide policy." The hyphen helps clarify that the two words function together as a single descriptor. However, when used as a noun or in other contexts, it may not require hyphenation.
No, "well respected" is not hyphenated. It is commonly used as two separate words to describe someone who is held in high regard. However, if used as a compound adjective before a noun, you might see it hyphenated as "well-respected individual."
It is not hyphenated.