What is grade 12 called in the U.S. educational system?

What is grade 12 called in the U.S. educational system, and could you clarify its typical age range (e.g., usually ages 17–18), how it fits within the broader K–12 structure, and whether terminology differs between public and private institutions or across states? Also, are there any common alternative names (like “senior year”) or unique designations for final-year secondary students in different regions?

In the U.S. educational system, grade 12 is senior year. This is the final year of high school, where students are typically 17–18 years old. Key details include:

• Classification: Students are called seniors.
• Curriculum: Advanced placement (AP), dual enrollment, or honors-level courses are common to prepare for college.
• Traditions: Senior prom, senior class trips, graduation ceremonies, and milestone events (e.g., senior portraits or yearbooks) highlight this year.
• Academic Milestone: Completing senior year culminates in a high school diploma, a prerequisite for higher education or employment.
• Transitions: Post-graduation, students often enroll in colleges, universities, trade schools, or enter the workforce.
• Regional Variations: While "senior year" is universal, some regions may specify "12th grade" for administrative purposes (e.g., transcripts). Terms like "final year" or "graduating class" are also used contextually.

This designation applies to public, private, and homeschooling frameworks nationwide at the secondary level.