What's the score with tax on second job if you're a student?

UK? You have a certain value tax free, you pay the lower rate of tax up to the higher tax bracket. It doesn't matter how many jobs you have - the first one takes up the no tax bit (unless you don't earn enough in which case the 2nd job takes the remainder of it) then the lower rate tax gets taken up by the 2nd job..... it is unlikely you will be on higher rate tax - hopefully.

All UK citizens, of whatever educational status, get a tax-free personal allowance of £6475, period 6th April to 5th April each year. You can sign form P46 at main job to say that's what it is. Your allowance will therefore be put to that job. You can't sign form P46 at second job, therefore employer has to put you on code BR (Basic Rate, 20%). You can however contact main employer's tax office, and ask for you allowance to be split between jobs, giving staff details of both jobs. Then amended code numbers will be issued, and 2nd employer will refund any tax deducted with next wage packet.