It was not bad but didn't improve my maths skills a lot to be honest...
They literally gave you sheets of addition, subtraction, multiplication and division to do and you sit there doing them with other students and you'd "level" up as well.
And then for English, that wasn't much use at all... simply learning the spellings of words and learning the definitions without actually putting them into practice was utterly pointless.
It was an alright experience but I wouldn't recommend it to others personally