The Collaborative International Dictionary of English v.0.48:
Mistaught \Mis*taught"\ (m[i^]s*t[add]t"), a. [See Misteach.] Wrongly taught; as, a mistaught youth. --L'Estrange. [1913 Webster]The Collaborative International Dictionary of English v.0.48:
Misteach \Mis*teach"\, v. t. [imp. & p. p. Mistaught; p. pr. & vb. n. Misteaching.] [AS. mist[=ae]can.] To teach wrongly; to instruct erroneously. [1913 Webster]