Not just Luiz, his brother Kyle was also getting so many attentions from his school mates but he only smiled faintly at them. Unlike Luiz, he was very open with his opinion and he already said that he won't be pursuing his modeling career. He even told his fans or his admirer to support his brother instead.
For Kyle, his teaching career was more important and he didn't want to give Kath the chance to be bothered with other women. She's already having low self-esteem with all the admirer he got before he became a model. How much more if he really chooses to become a model? He didn't have the heart to hurt her.
They also talked about it and even though Kath agreed that he will become a model, he also knew that she will be jealous of those female models that he will be working with and because of that he chose her over his modeling career.