Nasau County District Attorney Denis Dillon says as the 1998 school year begins it is important for parents to take certain precautions to protect their children from becoming crime victims. Out of every 100 children between the ages of 12 and 19, 13 will be the victim of a theft each year, according to the Department of Justice. That's better than a one in 10 chance that your child will have his or her jacket, sneakers, skateboard, radio or even lunch money stolen, not to mention his or her bicycle.

To avoid being the victim of a rip-off, here are some suggestions from the National Crime Prevention Council:

- Don't give your child a large bill for school lunches; he may be seen getting change, followed and robbed. Give him the money he needs a day at a time.

- If he is robbed, tell him not to resist; no amount of money is worth a beating. Encourage him ahead of time not to hesitate to tell you if it happens.

- Show kids the safest walk home from school, one that avoids seedy or wooded areas, if possible. Remember that children often love to find back roads. Explain to them why you don't want them to take them.

- Organize a buddy system with the children of neighbors for the daily walk.

- Consider a Block Parents program. Parents designated on each block display a sign in their windows that indicates to passing school children that someone is at home and available if anyone frightens or accosts them.

- Know the school bus drivers and crossing guards. Encourage children to greet them by name every day. If your child is frightened tell him to stay with the guard until he feels it is safe to continue home.

- Suggest that easily stolen items, such as radios, be left at home. If he insists on taking them to school, tell him to keep them locked in a locker and not to reveal the combination to friends or write it in an obvious place such as the front of a school book.

- Get the best bicycle lock you can buy and demonstrate how to thread it through both wheels and around a stationary object. The plastic-covered chain type can be cut with a small tool. It is wiser to invest in a U-shaped, all-metal padlock. Borrow an engraving tool from the local police and mark the bike with your driver's license numbers so it can be traced through police computers; record the bike's serial number for identification if it is stolen.

- Warn teenagers to leave nothing in their cars. Drug users often rifle automobiles looking for drugs and steal whatever they find. You can buy removable stereos and tape decks, which can be kept in the school locker during the day.

- Protect your child from so-called "friends" who may, while they are guests in your home, steal his possessions or yours. Know the kids your son or daughter hangs out with as well as their parents. Impress upon your child that certain rooms in the house are off-limits to visitors.

Kids over the age of 15 are assaulted more than twice as often as adults are, according to the Department of Justice. And 40 percent of these assaults occur in school, compared to 36 percent on streets, parks or playgrounds. Almost 300,000 high school students are attacked every month at school. The victims may never even report an assault because they don't think anyone will pay attention - which, sadly, is often true.

Something can be done. Most attacks are at the hands of a very small group of habitual juvenile offenders; an assault you report goes on the offender's record even if no conviction takes place. Therefore, even limited police involvement may prevent future attacks.

Students as a group can apply pressure on the few responsible for the violence.