Crash higher maths

Honestly I wouldn't recommend crashing H Maths, a lot of things from N5 are needed to form the absolute basics of the Higher course. This is the case even more so than pretty much every other subject.

How good are you at maths at the moment? If you are serious about crashing maths, have a look at National 5 resources (BBC Bitesize is pretty good, I don't know about any textbook/how to pass guides but I'm sure they're about) and maybe even try the N5 2014/15 (& 16 when it comes out) Past & the 2014 Specimen Papers.
I imagine you'll have some trouble convincing your maths teacher (& head of department especially) to let you do it though, if you do well in the N5 exam/specimen papers you could show this to your teachers to show that you are capable of at least passing N5 and that you are willing to put the effort in.
What course/uni are you looking at right now, and what qualifications/grades to they need.
Finally, what year are you going into now? And how quickly can you learn things?

Thanks for the reply! And yep, I thought I'd struggle to convince them too, it's probably best to do nat 5 next year instead. And I'm going into 6th year, so I can't work my way up by doing nat 5 then higher. I thought instead maybe I'll just do nat 5 this year and do 2 advanced highers instead, If I need the third advanced higher to get into my 1st or 2nd choice university I suppose I'll just do a gap year and get the qualifications then. Thanks for the help, I really want to do well in the advanced highers so I don't want to be slack with them because I'm crashing higher maths.