The best way to improve students' interest
提高学生（对.）的兴趣的最佳途径
in a subject
对一个学科（或课题）
is
是
to teach them the significance of the subject outside the school.
教（指出,讲授,教导）该课题的校外（非学术性）的意义（和用处）
放在一起：（意译）
The best way to improve students' interest in a subject is to teach them the significance of the subject outside the school.
提高学生对学科或课题的兴趣的最佳途径是教导和指出该课题的校外的、实际上的更深层意义和用处.
希望帮到了你,满意敬请采纳,谢谢.