NMACS IN TFC PATTERN.

Narrative

WHILE CONDUCTING FLT INSTRUCTIONS L HAND FOR RWY 15 AT RENTON ARPT. I WAS FOLLOWING AN ACFT ON FINAL WHEN A PATTERN HIGH WING. ACFT FLEW BTWN ME AND THE ACFT ON FINAL ON MY L SIDE; THEN CIRCLED AROUND BEHIND ME TO THE R AND ENTERED THE PATTERN BEHIND ME. IN THE CONFUSION THAT FOLLOWED; I WAS FORCED TO GAR AT ATC'S REQUEST. BECAUSE OF THE TOTAL WT OF MY CRAFT AND HP; IT WAS SOME TIME BEFORE I COULD ACTUALLY START TO CLB AFTER INITIATING THE GAR. (THE FACT THAT MY STUDENT FROZE AT THE CTLS DID NOT HELP) AS I WAS ATTEMPTING TO GAR; I SIDE STEPPED L AND NOTICED THE ACFT BELOW AND AHEAD OF ME WAS DOING TOUCH-AND-GOES AND WAS LIFTING OFF AND LOOKED TO BE TURNING L (INTO ME IN THE CLB). BECAUSE I KNEW THE PLT IN THE PLANE; I INSTRUCTED HIM TO STAY DOWN (LOW) AS I KNEW HE COULD NOT SEE ME AS HE WAS IN A HIGH WING ACFT. THIS WHOLE MESS STARTED DUE TO SOMEONE ENTERING A PATTERN WITH ATC PERMISSION WHEN ATC DID NOT KNOW EXACTLY WHERE THEY WERE AND ENTERING A PATTERN IN A NON STANDARD MANNER AND LOCATION. ATC SAID OVER THE RADIO 'SORRY FELLAS; I'M HAVING A HARD TIME SEEING YA DUE TO THE HAZE.' IF ATC CAN'T SEE MORE THAN 1/2-3/4 MI DUE TO HAZE; THEN THE FIELD SHOULD EITHER BE CLOSED (IMC CONDITIONS) OR NON STANDARD PROC SHOULD NOT BE USED! AS IN THIS CASE; IT STARTS A CHAIN OF EVENTS. ACCIDENTS ARE NOT CAUSED BY ONE BIG MISTAKE BUT MORE BY A COLLECTION OF SMALL INCIDENTS/MISTAKES. IN THIS CASE 1 EVENT CAUSED A CHAIN OF EVENTS. THAT ALMOST CAUSED. 2 MID-AIRS WITH 1 ACFT IN LESS THAN 2 MINS.