I'm one of the fustrated teachers who is expected to suddenly know how to programme when my background is ICT. I've spent a fair few months learning python and have what I feel is a good understanding of it. I then tried the new controlled assessment tasks on interchange for the new Year 10s in September. The troubleshooting one started off easy and ended up a nightmare of loops. I then moved on to the barcode one which so far seems much simpler. I *think* I have a working solution which I obviously won't put on here as to break exam regulations but I wonder if someone can give me an INCORRECT GTIN to test my program with as every number seems to be a valid one (even when I calculate it manually). Granted...I may be doing something daft! They all seem to be a multiple of 10 when doing the validity checks.