Psychology Stats Report Help Please

#1
Hi there,

I'm currently working on a statistics report for a project in psychology.

I've collected two lots of data: test scores on two different units of an A-level course: one group is only taking two other subjects, and a second group is taking three subjects.

So essentially: 2 groups (20 in each) and 2 scores per subject.
I want to compare if there is a difference between the two groups, and also whether the students performance changes between units.

My problem is that I am unsure what statistical analysis/ tests to be using? I thought of doing a t-test, but I'm not 100%. I will be using SPSS to do the tests.

Any help would be greatly appreciated :)