Lucas (1986) on Netflix

Lucas is a promising kid, bright, inquisitive, knowledgeable, industrious, but for a boy aged 14 those qualities don't count for much socially, his daily life in high school is a brave but hopeless struggle against cruel ridicule (nicknamed 'leukoplakia') and abuse on account of his frail figure, 'miniature' size and athletic ineptitude, while any demonstration of precocious erudition is frowned upon by his ignorant, dumber peers and seniors, fortunately with one remarkable exception: the studly football team captain, generally known as Cappie, gallantly protects the 'shrimp' and as soon as he gets to know Lucas appreciates his mind and courage, eager to learn from him. The arrival of an attractive new girl in his school and neighborhood proves a mixed blessing: Maggie becomes his best friend and companion, admiring his many talents, but inevitably she soon falls for Cappie the other way, so now his 'big brother' and protector seems little Lucas's rival, however hard the hunk tries to stay friends...