"can" is a modal, so the following verb does not take "to" or "s").
The teacher wants to go home at 4 pm.
The teacher can go home at 5 pm.
Verbs of sensation (see, hear, taste, ...) don't normally have an -ing form for an action in progress. "Can" gives the meaning of an action in progress.
The teacher talks to the students every day. [repeated action]
The teacher talks to the students. [repeated action]
The teacher is talking to the students. [action in progress in the present]
The teacher hears students in the hallway between classes. [repeated action]
The teacher is hearing students in the hallway. [<< incorrect]
The teacher can hear students in the hallway. [action in progress in the present]
The teacher hears students in the hallway. [ambiguous, meaning depends on context - repeated action or action in progress?]
More information:
English Grammar in Use by Murphy, Unit 26 "Can, could and (be) able to"