I have a study i am running and would like to know the appropriate test to apply, its complicated but bear with me

We are looking at assessing the effect a series of optional tutorials delivered during a semester has on test scores in a cohort of students. There will be a total of 9 tutorials delivered, attendance will be recorded. As students will be allowed to attend of their own free will, strict control vs intervention groups will not exist (we cant say 1/2 of cohort must attend all 9 and other 1/2 cannot attend any sessions). Instead, a minimum attendance (e.g 2 of 9 sessions, 3 of 9 sessions, this has yet to be decided), will be chosen as a threshold for entry into the intervention group. We may later do an 'intention to treat' analysis to see if greater attendance correlates with higher scores for within group analysis.

50 Students were given a 20 MCQ exam, 1 mark per question answered correctly. They were allocated to either Paper A or Paper B (both 20 MCQ each), 25 students per paper. Testing was mandatory for all students to attend (50 of 50 attended). Results were as follows

Paper 1. MEAN: 11.32 MED: 11 SD: 2.39
Paper 2. MEAN: 10.56 MED: 10 SD: 2.75

Then ran a few tests to check for equal variances, difference between means and if the data followed a normal distribution, all were not significant thankfully

Variance - F Test
Difference between means - T Test
Data follows normal (Gaussian) distribution -D'Agostino-Pearson omnibus test

The 2nd test period is due to occur in June. All students given Paper A will be given Paper B and vice-versa (cross over).

So now i am wondering....

If i am to measure the test score difference between the intervention group (e.g. attended minimum 33% of sessions), and the control group (attended < 33% or no sessions), can i use an ANCOVA if the pre-test scores come from separate tests (A and B) that have been deemed to not be statistically significantly different from one another (p=0.303)? Would this be the best test to use?

Any help would be much appreciated!