Like others have said, if you do try blm/sch i would stay in dark arts mainly. Being in the correct arts lowers cast and recast times as well, also, casting in the incorrect arts hits you with a cast/recast and mp cost penalty. Also, if you are in light arts the whole time, you won't have access to the two dark arts strategems, which are very handy.
One thing i have to mention tho is that the reason that /sch is not immensely popular with blm's is the lack of defensive spells. It may not be as big of a deal early in the game or for party play but at mid to late levels and for all types of solo play, your going to want some defense. By defense i mean two spells mainly... Blink and Stoneskin. These two spells add a great deal of survivability to blm, i can't count the number of times they have saved me from a dirt nap. My point is that /sch doesn't give access to them, only /rdm and /whm.
Do what you like but you'll find out eventually that there is a reason that /rdm and /whm are the two main subs for blm.
Oh, and by the way, welcome to FFXI :)
BLM75 RDM75 SCH75 BLU75
CoP: Done / ZM: Done / ToAU: Done