Summary:
Lyme-Old Lyme High School is the sole high school in Regional School District 18, serving grades 9–12 in Old Lyme, CT, with 367 students and a strong record of academic achievement.
This one-school district offers a consistently high-performing high school. On recent state tests, Lyme-Old Lyme High School has far outperformed Connecticut averages. In 2024–2025, 91.9% of 11th graders were proficient in ELA (compared to 58.0% statewide), 70.9% were proficient in math (versus 31.1% statewide), and 80.2% were proficient in science (versus 47.7% statewide). The school also earned 5-star ratings and ranked 4th in Connecticut in 2024–2025 and 7th in 2023–2024. More recent 2025–2026 data show some decline: ELA proficiency fell to 80.0% and science to 72.9%, still well above state averages, but the school dropped to 22nd in the state and a 4-star rating. Its graduation rate is 92.9%, slightly above the state’s 91.2%. With a low student-teacher ratio of 9.6:1 and only 12.81% of students qualifying for free/reduced lunch, the school benefits from substantial resources. Per-student spending was $22,213 in 2018–2019.
A notable concern is chronic absenteeism. At 19.8%, it is higher than the district rate of 10.1% and the state rate of 16.4%. This is surprising given the school’s strong academics and may be worth monitoring, especially as test scores have slipped from their elite levels. The missing math data for 2025–2026 makes it unclear whether math proficiency also declined. Overall, Lyme-Old Lyme High School remains one of Connecticut’s strongest high schools, but parents should be aware of the recent dip in test scores and the elevated absenteeism rate.
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