The school, via the CFI, has to recommend you for a test. For many schools, their first time pass rate is a factor in whether they may keep their Air Operator's Certificate's flying school licence. No school is going to recommend you for a test unless they have a reasonable belief that you will pass.
When I was a CFI, the best way I found to assess that likelyhood was a pre-licence test ie a ground & flight exercise that, as much as possible, replicated the real thing. It didn't cost the student any extra $ because I included the pre-licence tests within the minimum hour requirements for each course.