I don't think it's a big deal... There's very little need to get an external assessment at this age level. It's a very time consuming process to prepare students for the examinations and frankly the time can be far better spent to actually teach students. Year 11 student basically lose 2-3 months of class time to prepare for these examinations. They are usually dismissed by April... and then a similar process for IB two years later. It's a serious overkill particularly in light of the fact that the IB results are what matters to get into university which represents the majority of ESF's clientele. The two systems really don't mesh that well together so it makes sense to get rid of the least useful one.
If students don't complete the full IB diploma, they can still get a certificate. ESF is a private institution, they are trying to compete with other schools in HK and have to take steps to remain competitive. They can't survive on expats alone and the biggest demand is to train students to have access to the best universities everywhere. That is best achieved with the IB program...
It is unfortunate that some kids will be left behind but there are other alternatives for the weaker students. If ESF was a public school, it would be a different story but it isn't...