Afternoon batch restarted after month-long break; concern area now the first two batches

The computer classes are coming out of an initial adjustment period. Our new teacher has been slowly but surely gaining familiarity with the students, the material and our practical & demo-focused teaching methodology. The students are largely being patient and getting used to this, but providing critical feedback in order to to help make the experience better for everyone.
The afternoon batch (2-4pm) was restarted mid-April after a month-long break while most students gave their exams (note: While none of the students are in college, nearly all of them are studying through correspondence). There has definitely been some loss of learning in that one month, and catch-up classes were taken to rebuild their understanding of fundamentals.
The effect of this month-long gap was probably most evident in the results of the Unit I (Fundamentals) test that was administered, with the Evening batch doing much better on average. Based on learnings from the first two batches, and brainstorming among GDL staff, we have decided to implement a dual test approach. Students are administered a surprise preliminary test after each unit. The results are then compiled, and general gaps identified. After covering these topics, the students are given the ‘real’ test within the week. This way, we ensure that students learn, and still meet our high standards for passing (currently at 80%).
The other main reason is that is also helps us avoid doing catch-up classes after the batch is over. Nowhere is this challenge more felt than with the first two batches, who finished their final exams just before college exam season started. The results show that only one student actually passed the course, and now it is becoming quite difficult to find a common time to bring all the students from these batches in, do catch-up courses with them and re-administer the tests.
Next week promises to be another round of tests, as well as our first set of structured one-on-one Personal Meetings, guided by the test results and a feedback form filled by the student.