In writing task 1, there will probably be one or two key words or phrases that you find yourself repeating in almost every sentence. For example, last week's graphs were about spending on sport and participation in sport, so it was necessary to mention these two ideas several times in the answer.
Add variety where you can
In my answer, I did try to add some variety where I felt that an alternative word or phrase worked well. For example, instead of "participation in" I also wrote:
- took part in
- taking part
- were enrolled in
But repetition can also be positive
I wasn't too worried about repeating the key ideas (spending and participation) a few times. I wrote "parents spent" three times and I used the word "participation" four times. It can help the coherence of your writing if a key word or phrase is repeated, because this helps the reader to make connections between ideas in different sentences. Too much variety can confuse the reader. For example, it will seem very strange if you use 10 different synonyms for a word like "spending".
Remember: variety is good, but repetition is also normal.