You should try
SELECT t1.uid
FROM tabl_1 t1 INNER JOIN tabl_2 t2
ON t1.uid = t2.uid AND t2.meta_key = 'location' AND t2.meta_value = 'NY'
INNER JOIN tabl_2 t3
ON t1.uid = t3.uid AND t3.meta_key = 'school' AND t3.meta_value = 'NYU'
Check result on http://sqlfiddle.com/#!2/f35ef/1/0