A school on probation means that something at that school did not meet ACPE standards. The school is given time to fix whatever problems it has so that when the next school visit comes, they can be taken off probation. However, the school is still accredited and you can still sit at the NAPLEX exam and get you license.
Probation does not mean non-accredited. If a school does not address its problem on probation, it can lose its accreditation and that would mean your license to practice would be no good (i think), but no school has lost its accreditation in the time of the ACPE.