Is this a sexual abuse?

There is no universal definition of child sexual abuse, but a central characteristic of any abuse is the dominant position of an adult that allows him or her to force or coerce a child into sexual activity. Child sexual abuse may include fondling a child's genitals, masturbation, oral-genital contact, digital penetration, and vaginal and anal intercourse, but also include non-contact abuse, such as exposure, voyeurism, and child pornography. Correctly diagnosing abuse is often complex, for that reason when abuse is suspected, an appropriately trained health professional should be consulted.

My advice would be that it is better to investigate all cases that could possibly be child abuse than to let one child be abused becasue we didn't want to push an investigation where we didn't know for sure it is needed.
If you are unsure, by all means, report it annonymously and let the athorities decide for themselves.

Its not sexual abuse. Hes just a perv. But if he tries doing anything to them, then it is sexual abuse and you should report him.

its not that bad, i mean hese starring hese not touching them plus hese a child going through puberty and hese getting hormones and changes hese exploring,, talk to co workers about it see what they say.