Honestly I was a little surprised at the cheating too. I think I was a little naive in the beginning that if you actually wanted a job you would understand that you would have to be able to write code. But some folks are in a school mentality that if you get a grade/diploma you're good, regardless of whether you understand the things required to go into that.

Having tried a number of different ways to do admissions, I can assure you doing interviews is possibly the worst.

As far as ISAs go, it all comes out in the wash. If you create a pool of ISAs and students don't get hired you may have more ISAs but the average ISA is worth less, so the only thing that matters is whether each individual student gets hired. There's no financial wizardry that can let you sell $1 for $2 in the long-run.