How to make algebra more engaging for 5th grade students?

I had a student come up to me last year (at the end of the year) thanking me for giving him a 100 on a test we had right before winter break, he averaged around 70 before that test... I admit, he should've gotten less, but I like to give students a higher grade from time to time to keep them motivated. His average went up significantly throughout the rest of the year.