Need to align 2 id numbers across files and then fill in corresponding column

I have student numbers in 2 separate files that I need to use to fill in whether or not they were absent which is in another column.

What is a formula I can use to ask Excel to find the same student id number from one file in another and then fill in another column?

For example,

H1 has my student id #. I need Excel to find this exact student id # in another file and fill in the corresponding row line from column S.

There are two functions to use: Vlookup and combined Index/Match. My preference in Index/Match: here's how it works. (1) Index the column that contains the information you need. Then match the unique identifier for the output with the unique identifier of the data set. Assuming the data you want to output is in column S, the student ID for the new data set is cell H1 and the student ID in the data set is in column A (cells 1 - 15), the formula would be:

=index(s$1:s$15,match(H1,A$1:A$15,0))