DEAR ABBY: Many times I have read in your column, "Go back to school no matter how old you are." I took your advice.

Three years ago, I had a choice to go on welfare or go to school. Since I didn't want to raise my children on welfare, I chose school. It was hard for me to think of going to school, as I had dropped out at 16 and didn't want to go back with a bunch of younger people. I started college and worked on my G.E.D. at the same time. I also found out that people of all ages went to school. Going back wasn't as hard as I thought it would be because it was what I really wanted.I'm proud to say that I will be graduating from the Mohave Community College on May 10 at the age of 36.

Please keep telling people to go to school. It's the best thing I ever did for myself. Thank you, Abby. - DEBI SMITH, LAKE HAVASU, ARIZ.

DEAR DEBI: Don't thank me - it was you who recognized good advice when you saw it, and you went for it! Congratulations.

DEAR ABBY: Our problem is mainly our daughter - I'll call her Cheryl. Her husband walked out on her seven years ago and left her with their 3-year-old daughter.

Although our home is small and we are getting up there in years, we took Cheryl and our grandchild in. She has never paid one penny toward their keep.

Cheryl has started to date again, and she expects my wife and me to take care of our grandchild. We don't mind, except that Cheryl comes in at 3 or 4 a.m., and when her boyfriend comes to our house she takes him upstairs to her bedroom. She also lounges around in her nightclothes and lets him put his hands all over her regardless of whether my wife and I are in the room. This goes on right in front of her daughter, too. What an example she is setting!

My wife's health is bad and she can't take much more of this. We have high morals and do not believe in sex outside of marriage. Cheryl says she's over 21 and can do as she pleases. We don't say much to her because it will only cause a fight. What do you suggest? - PROBLEMS IN ST. LOUIS

DEAR PROBLEMS: Tell Cheryl that although you can't tell her what to do, as long as she is living under your roof she will have to abide by your standards - which means no entertaining her boyfriend in the bedroom.

If your demands will cause a fight, so be it. But unless you put your foot down now, nothing will change. Cheryl will not easily give up the free room and board for her and her daughter, so when you deliver your ultimatum, stand firm, and do not give an inch! I wish you well.

People are eating them up! For Abby's favorite recipes, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada), to: Dear Abby, Cookbooklet, P.O. Box 447, Mount Morris, IL 61054. (Postage is included.)