100 points in 1.5 months. I have seen it before but it's pretty rare. I see 50 point jumps all of the time. Your ability to jump 100 points in 1.5 months in a function of what you've done to this point and how much time/money you will dedicate to this over the next 1.5 months.
What was your score on your first practice exam and when did you take it?
How many hrs/week have you been studying?
How many hrs/day do will you spend studying over the next 1.5 months?
How much budget do you plan to dedicate to score improvement? (on a scale from a modest amount --> whatever it takes)
You also may need to look at the possibility of applying next round/year. It is possible to hit 100 points in that time frame, but it all likelihood you will need a bit more time.
I don't know if anyone does trials for Private Tutoring...
I have been studying every day, almost with no day off (maybe only a handful) from almost 1/9 to 1/10 and from 15/10 till my exam day. Usually from morning till 7pm at night, with 1 or 2 hour breaks throughout the day. So I'd say in average 5 hours a day. Before that, I was trying to study a few days a week, though I was too tired coming back from work. However, going back to my first point, I think I'm overlooking several points. Also, following OG13 and this forum, I had my own perception of the test's difficulty, which proved to be far from the real thing. For example I have been overlooking questions which I considered to be too hard or lengthy both in gmartclub and MGMAT's question banks and CATs.
My MGMAT's CAT and some GMATPrep attempts (which are inflated as time goes by) are as follows:
Q44 V31 Total 610
Q37 V28 Total 540
Q39 V28 Total 550
Q45 V19 Total 530
Q47 V30 Total 640
Q37 V29 Total 550
Q48 V25 Total 600
Q38 V26 Total 530
Q49 V33 Total 680
Q42 V35 Total 640
Seeing that now it's no surprise that I got 580, however I was hoping on the fact that I could at least get a 620-630 on my first attempt, based on the last two tests plus the fact that the real gmat quants are somehow easier than MGMAT's and verbal is about the same. I got Q39 V31 in the real test.
Also, back in August I got a 550 in GMATPrep (one of the first ones) which compared to my actual GMAT is very little change, as if I have made no progress. However I very much feel that I have done significant progress in all sections especially in SC and CR, though that doesn't reflect.
My budget is along the lines of what all the major companies are offering for 10-20 hours, but again, I don't know how that would translate to my actual progress. My thinking is that a) it can't make me it any worse, and b) it's an investment afterall and I really want to do this so I am willing to take every step that I need.
I was thinking of applying for Sept 2014 programs, what do you mean when you say next year?
Also, this 1.5 months (maybe 2 even) I can dedicate full time into studying.