I'm doing some essays to prepare for the C1 writing test. I wrote this sentence:
"after a student had understood a formula, it would be more efficient if he was able to apply it through experiments in a laboratory class"
But I'm not sure whether I should use had or has understood. My point is exactly that the educational system is focused merely on mnemonic knowledge in scientific subjects, while it should be more practical. So I want to say that it's better when a student first learns something in theory, and then is put in a position to apply his/her knowledge in a lab.