Based on the admissions policy, it really shouldn't be that hard to transfer into MACS.  As long as you are in good standing at current school system, MACS have room/class space, release from the BOE of their current school, and approved reasoning to transfer (basically anything other than athletics, but realistically what parent is dumb enough to use that as their reasoning).   
Tuition Rates:
In County - $200, each additional child $100
Out of County - $600, each additional child $300
Out of State - $1320, each additional child $660
A quick google search and I found that info.  Doesn't seem like it is too difficult or expensive to transfer in from the surrounding areas.