primary school
1 (Brit) first school for children of (usu) 5-11 years 小学(儿童年龄通常为5至11岁).
2 (US grade school, grammar school) part of an elementary school, for children of (usu) 6-9 years 初级学校(小学之初级阶段, 儿童年龄通常为6至9岁).
Shortly after this the famous H. M. S. Challenger expedition established the study of the sea-floor as a subject worthy of the most qualified physicists and geologists.