Pretty much any school can do it. As could any stand alone instructor. Or even none if you can find an aircraft to rent. You don't *require* an instructor recommendation to sit the test if you hold an ICAO CPL or ATPL but are unlikely to pass without some training & familiarity with the USA way of doing things.
Make sure your hours meet the FAR min. experience requirements. Be careful about what may counts as x-country time for the ATP.
Buy or download a copy of the FAR/AIM & get familiar with the contents. There are some significant differences. US uses TERPS, not PANS-OPS for procedure design so some things are different eg circling areas, time the inbound of a holding pattern then adjust outbound timing to make the inbound time correct.
Buy or download a copy of the ATP Practical Test Standard. Also Jepp, ASA et. al. have guides to passing the oral portion of the checkride.