Is it true that if All of the students in Mr Osborne's class like pizza and Jeff is a student who likes pizza that Jeff is a student in Ms Osbourne's class?

Not necessarily. The statement only establishes that all students in Mr. Osborne's class like Pizza, but it does not specify that liking pizza is a requirement to be in his class. Jeff could still be a student in Mr. Osborne's class, but it is not a definitive conclusion based on the information provided. Additional information would be needed to confirm Jeff's status in Mr. Osborne's class.