SQL select from 3 tables with 3 different ordering (NO JOIN)

I have 3 tables: Students, Teachers and Courses. I need to SELECT 3 youngest students, 3 oldest teachers and 3 longest courses. I don't know how to set 3 different ordering for every table.

I need something like:

SELECT Students.name, Teachers.name, Courses.name FROM Students, Teachers, Courses ORDER BY Students.age, Teachers.age DESC, Courses.duration LIMIT 5;

With a result like:

Student_name | Teacher_name | Course_name

Max. Steven Design Bill. Dave. SQL Paul. Alex. Python

But it doestn't works...

Can you help me please?