SUMIF Children, Referencing Another Sheet

I am creating a summary sheet and would like to include a sum of course developments by college. I know how to do a SUMIF in general, but can I use the CHILDREN function to sum (or count the number of instances) of courses/payments based on the value in the College column?

Source Sheet

The parent is called 201910, and all of the courses are listed as children, under this parent. College values can be PS, KC, ED, or UG (Col 6).

Summary Sheet

1. I want to COUNT the number of courses on the development list for each college (so count the course if the course is associated with a particular college (Col 6). what is the total number of courses for PS, KC, ED, and UG?
2. I want to SUM the amount of payments (Col 15) to SMEs working on courses associated with a particular college (Col 6).

I assume the structure of the COUNTIF or SUMIF is the same, I am just stuck on how to use the CHILDREN() function as I reference a different sheet.

Thanks!!!