Table schema:
CREATE TABLE table_name_23 (evaluation_average__before_april_2009_ VARCHAR, peak_lessons_taught VARCHAR, _percentage_of_negative_evaluations VARCHAR)

Question: What is the mean Evaluation number (before April 2009) when the Peak lessons taught was less than 80 and the negative percentage of evaluations was 0.8%?
SQL: SELECT evaluation_average__before_april_2009_ FROM table_name_23 WHERE peak_lessons_taught < 80 AND _percentage_of_negative_evaluations = "0.8%"