Answer - If you go to Reporting>Reports>Students (Blue Tab) and use the Birthdays report - entering the dates needed, this will create a report with all birthdays in a given timescale. If you want to check who is going to be a certain age i.e. 5 years old - go to the new age column and in the empty white box, under the heading enter the age, this will give you those children who only have that age.
If you require a report that shows student ages in years and months, then go to Reporting > Reports > students (tab) > Date of Birth. This report will give you the student name, year, form, address, birthday and current age in years, months and days.