Improve the bracketed part of the sentence.
The teacher as well as (the students are) distracted.
When a subject is joined with another subject by “as well as”, “along with”, “in addition to”, etc., the verb agrees with the First subject. The first subject or the main subject here is “The teacher” so “is” will be used here. Also, the definite article “The” will be used with students because it has been used with teacher.
You can’t say the teacher as well as students.
Thus, the correct sentence is: The teacher as well as the students is distracted.