Are you taking International A levels? If so you don't have to worry about the practical endorsement - these are a series of practicals which students doing the UK A levels in sciences have to do in class and pass (although you can be awarded the A level without it most unis want you to have passed it). The International A levels have a written paper about practical skills instead. Also the International Maths A level lets you choose the modules you want to study, but the UK one doesn't any longer.
If you are taking International A levels I assume you are living abroad, as you can't take them in the UK