I think one translation might be:
"By skilled teaching the character/intellect is formed"
a fitting motto for a school.
has the common meaning in classical Latin of education or teaching;
In medieval ecclesiastical contexts, "disciplina" could mean the scourging or chastisement which monks and others often underwent, but in a school context it seems to me more natural to think in terms of its classical Latin educational meaning rather than assume the school motto was intended to refer to the value of ruthless corporal punishment.
"sollerti" is the ablative of "sollers" which can be translated as skilled, clever, adroit or expert;
"fingitur" is singular present passive indicative of fingō, meaning something like: to shape, to form, to create.
"ingenium" often has the sense of character, disposition, way of thinking, ability, talent or intellectual capacity.