Data Validation Problem

I have a spreadsheet containing the dental records for 230 poor Mexican kids. I am trying to compile data for a 5 year study that some volunteer dentists are running. I am trying to generate individual dental charts by using the data validation function. I am 63 yrs old and Excel is Greek to me but I persevere! I need help because I have had to double the number of kids on one sheet (representing one grade level) and I can't figure out how to expand the drop down list that is generated by the data validation function; it only looks at the first 20 entries instead of the newly expanded 45 entries (an entry being an individual kid). A very nice person from this forum helped me out last year in designing the function. Somewhere there is a command that tells the data validation function to look at each sheet's entries but I cannot find it. The next clinic is next month and these dentists want me to have the data done by then. I am at my wit's end looking for this command but I can't find it. Can another compassionate, patient person please walk me thru how to correct this? I have hours and hours of work in they spreadsheet and right now, it won't do what I need it to do. Thank you in advance.!

Wow!! That looks great!! This is only a five year study, but thank you so much for expanding it!! Things may change in the future, you never know!!

Can I delete the list of class names on the summary sheet?